One week, three profoundly disturbing cases, and a few burning questions.

First the incidents. Let me start with the least publicised. A 51-year-old white man tries to enter a predominantly black church in Jeffersontown, Kentucky. But when he can't get in, he goes to a nearby supermarket and shoots dead two elderly black people. It is being treated as a potential hate crime. The man in detention also had a history of mental illness and shouldn't have been able to own a gun.

Then we have had the pipe-bomber who mailed viable devices to prominent Democrats and Trump critics; the first was sent to George Soros, a wealthy financier and philanthropist - who for some on the right seems to be the ultimate bogeyman, to be held responsible for when it rains too much and for when there's a drought. He is also Jewish. The rest were sent to the most senior Democrats in the country. Luckily no one was hurt. The man being held is a fanatical Trump supporter who was a regular at his rallies.

And finally we had the murders of 11 Jews at a suburban synagogue in Pittsburgh where worshippers had gathered for the Shabbat service and what should have been the joyous moment of a baby naming ceremony as a newborn is welcomed into the community. The gunman was heavily armed, and had a long track record of peddling anti-Semitic bile.

I should say I wasn't in the US last week. I had gone to a conference in Berlin, and while there I took a couple of extra days to do something I have long felt I must do, and have always dreaded. I went to bow my head at one of the concentration camps - Sachsenhausen - where thousands of Jews, Roma, dissidents and homosexuals were murdered during World War Two. It was every bit as bleak and chilling as I thought it would be. Actually a good deal more. And it was cold and rainy and the wind blew across the vast parade grounds where the inmates were forced to stand for hour after hour in the depths of winter in their striped pyjamas, as their Nazi guards looked on with indifference, all the time keeping meticulous records of those they had killed.

Media caption"It's a horrific crime scene. One of the worst, and I've been on plane crashes"
I returned to our comfortable, warm hotel so pleased to get my hands on a nice cappuccino. And I really did think how blessed we are to live in our liberal democracies in the West; to have grown up in a society without war, where we have freedom of expression, the rule of law, a free press and where there is tolerance and respect. I flew back from Berlin on Friday night. On Saturday came the Sabbath massacre.

I still happen to think we are immensely lucky to live when we do. But I have come back this weekend more convinced than ever that we must never forget what happened, and that there is zero room for complacency about the trajectory of our own society. Hatred lurks in its darkest corners and recesses, so surely it is the duty of everyone - from the president downwards - to realise that language that cranks up the resentment, that feeds the fear and loathing will push more people into actions driven by hate.

It would be easy to take the three incidents of the past week and create a narrative that America has embarked on a one-way journey towards nihilism. That the deep fissures in society are irreparable, all fed by the worst aspects of venomous spitting on social media. But as I reflected on what I wanted to write in this piece, I did what I normally do - I took the dog for his morning walk. At the end of my street is a park, and at the furthest edge of the park is a deep cutting which goes down to the Rock Creek Parkway. Normally all you can hear rising from below is the sound of traffic.

Today it was different. There was cheering and there was music. Intrigued, I walked down. And there set up on the side of the road was a band playing passable cover versions of one of my favourite bands, Steely Dan. And there were thousands of people lining the sidewalks and thousands on the road running their hearts out (or maybe lungs - anyway you know what I mean). Today was the Marine Corps Marathon in Washington. And it was fabulous. There were runners of every shape and size, there were the wheelchair athletes, there were black and white, Jews, Christians, all faiths and none, diehard Trump supporters and diehard Trump haters. But everyone on the road was there to run the fastest they could to raise money for the cause of their choice. And everyone cheering was there to offer support.

It is way overdone to just condemn America as some kind of dystopian hell. In everyday life people rub along, worry about their kids' schooling, want to provide for their loved ones and play their part in the community. They work hard, go to church (or synagogue or the mosque) and they - for the most part - are extremely polite and respectful to one and other.

One of the people I was with in Berlin last week was the former US secretary of state, Condoleezza Rice. She argued that what Americans need to learn to do is separate the president's rhetoric (broadly unhelpful) to the reality of what he does (broadly good, she argued). She also insisted that America in the 1960s was a far worse place - three political assassinations, the Vietnam War, cities burning and bitter racial division. That eclipsed anything being seen today, she said.

But like a low oil pressure light flashing on your car's dashboard that should not be ignored, so there are warning signs that America and the rest of the West need to take heed of. America has become more polarised - and that is partly a function of political rhetoric that has been amplified by the likes of Twitter and Facebook. Donald Trump was brilliant as a campaigner in highlighting division. His rhetoric at rallies fires up the base, and his supporters adore him. They love that he is a pugilist - if you hit him, you know he's going to hit back harder. But it leaves those who dislike Trump disliking him even more.

And of recent events he says he wants to be a unifier, but at the same time he says he has to attack the media and everyone else. I tweeted in the middle of the week that I thought it was regrettable that the president tried to place all the blame for the division in America on the media, and I equally said I thought it was regrettable that CNN's CEO had chosen to attack the president.

And as I might have predicted, I was roundly attacked for suggesting any fault lay with the president and condemned for suggesting that any blame lay with CNN. And that was not an attempt at "symmetry of guilt" - in other words they are all as bad as each other. I don't think that. But if all sides agree there is a problem then maybe all sides need to sit down and see whether there can be a more respectful, less hate-drenched dialogue. A little less eye for an eye, a little more turning the other cheek.

The reaction to the first reports of the pipe bombs was frankly incredible. Surely when explosive devices are being sent to the former president, former secretary of state, a former head of the CIA, a news network and a pair of wealthy Democratic Party fundraisers - the only reaction is to condemn and urge that those responsible are brought to justice. But the president in one tweet spoke of "this 'bomb' stuff" - a phrase that delighted the conspiracy theorists that somehow it wasn't that serious.

And that led to a lot of Trump surrogates talking the language of conspiracy - that this "bomber" was somehow too convenient - and maybe the person sending the bombs was a Democrat. Frank Gaffney, a well known right-wing commentator, tweeted: "None of the leftists ostensibly targeted for pipe-bombs were actually at serious risk, since security details would be screening their mail. So let's determine not only who is responsible for these bombs, but whether they were trying to deflect attention from the Left's mobs."

Now there is a lot to unpack there - not least the idea that it wasn't really that serious because it would have been the security guy or gal in the mailroom that would have been blown up and not the principal target. But the suggestion that somehow Democrats had done this to deflect from Donald Trump's attack on "the mob?" Really? If Democrats were that cunning and well organised they'd have campaigned a bit in Wisconsin and Michigan in 2016, states they critically lost and largely ignored. This is nonsense and deflection. If bombs are being sent it is an assault and affront to democracy. You don't need weasely ifs and buts. You just need straightforward condemnation

And I'm sure the president is 100% sincere in his hatred of anti-Semitism - and that is shared by those around him. His son-in-law is an orthodox Jew and his daughter Ivanka has converted to Judaism. But the attacks on George Soros just do smack of old-fashioned, Zionist conspiracy, blood libel stuff from history's darkest periods. I've read this week he is funding the caravan of illegal immigrants moving up from Mexico towards the US border. Anyone care to furnish a shred of evidence to back that up? His biggest philanthropic concern is to help former parts of the Soviet Union adapt to becoming liberal democracies. How is it that the attacks on Soros, once the preserve of the outer fringes of politics, have now migrated into the mainstream, with the president and his son Donald Jr regularly referencing him in speeches in the least flattering terms.

As I say responsibility goes from the president downwards. No one gets a free pass. He is no longer campaigning. He is the leader of the nation, the head of state. His words of revulsion at what unfolded in Pittsburgh are to be welcomed. In a lot of what he said he struck the right tone.

Now to the burning questions: some familiar, some newer. There are the inevitable "gun" questions. The president suggested yesterday that if only there had been an armed guard inside the synagogue, then it all might have been different. Well forgive me for saying, but four heavily armed and extremely well trained SWAT team officers went in and were shot trying to stop the carnage. You think one guy with his prayer book in one hand and a revolver in the other would have made the difference? And in Kentucky how was a man with mental health issues able to get a gun? As I say, these are well worn questions, and it is nigh on impossible to believe that anything will change.

But on the hatred that permeates so much of American political dialogue? The president has taken a lead, and seems to recognise the need for making moves towards becoming a unifier. Good luck, Mr President. But he is also campaigning like crazy ahead of next week's mid-terms - and he knows better than anyone how attacking his enemies is what delights his audience most. Let us hope that maybe something good can come out of the terrible killings at a Pittsburgh synagogue, and that it will serve as the wake up call that America needs. But I am not holding my breath.