Perhaps it might be useful, as we contemplate the horror of the murder of Drummer Lee Rigby of the Royal Regiment of Fusiliers in Woolwich on Wednesday, to have a quick look through the history books.
In 1971, for example, Robert Campbell killed 15 people in a bomb attack on McGurk's bar in Belfast. He was not a Muslim.
In 1984, the then Indian prime minister Indira Gandhi was shot dead by two of her security guards, Satwant Singh and Beant Singh. They weren't Muslims either.
In 1991, a suicide bomber named Thenmozhi Rajaratnam blew herself up and killed Indira Gandhi's son and heir apparent, Rajiv. She was not Muslim.
In 1994, Baruch Goldstein opened fire in a mosque in Hebron, in the West Bank, and killed 29 Palestinian worshippers. As you might have guessed, he wasn't a Muslim.
In 1998, 29 people were killed in a bomb attack in Omagh, in northern Ireland. Not one of the bombers was Muslim.
And yes, I'm coming to it, in 2001, a group of hijackers killed nearly 3,000 people in New York, Washington and Pennsylvania. All 19 of the hijackers were Muslim.
As were the attackers who killed more than 200 people in Bali in 2002, another 200 in Madrid in 2004, 52 people in the London bombings of July 2005, and 160 in Mumbai in 2008.
Oh, and while I'm at it, in 2011 Anders Breivik killed 77 people in Oslo, and last December, Adam Lanza killed 26 people, most of them children, at a school in Newtown, Connecticut. Neither Breivik nor Lanza were Muslim.
You see my point, don't you? There's nothing "Islamic" about acts of violence. So all those anguished questions along the lines of "What is it about Islam that drives people to such terrible acts of violence?" seem to me to be entirely specious.
Of course, there's a tiny number of Muslims who say they carry out acts of violence in the name of their religion. Just as there are some Christians, Jews, Hindus, Sikhs, and - as we've seen in Burma - even Buddhists, who say the same.
We will learn more in the coming days about who the alleged Woolwich attackers were and the background to what appears to have been an unusually brutal attack. For now, though, the clearest pointer comes from one of the alleged assailants themselves.
According to the account given by the remarkably courageous Ingrid Loyau-Kennett, who confronted them within minutes of the attack: "I asked him if he did it and he said yes, and I said why? And he said because he [the victim] has killed Muslim people in Muslim countries, he said he was a British solider and I said really and he said 'I killed him because he killed Muslims and I am fed up with people killing Muslims in Afghanistan, they have nothing to do there.'"
Now, there are many people who object to US and British policy in Afghanistan and in other Muslim countries such as Iraq, Somalia, Yemen, Libya, and Syria. Plenty of Muslims and non-Muslims alike have been sickened by images from Abu Ghraib prison in Baghdad, or showing soldiers posing and gloating over the bodies of dead "insurgents". They may be deeply opposed to the Obama administration's use of drones to kill "high value targets" in Afghanistan, Pakistan, Yemen and Somalia - but they don't go out onto the streets of London or New York to kill soldiers.
So it seems to me there are two tough questions that need to be asked: first, can anything effective be done to reduce the number of vulnerable young men who are likely to be persuaded by the sort of propaganda that leads them to commit acts of violence?
Second, does it make sense to go on pretending that these acts, when they occur, have nothing to do with government policy? It may or may not have been right for Britain to join with the US in invading Afghanistan and Iraq, but can we honestly claim that British military action in those countries has had nothing at all to do with the radicalisation of a tiny handful of young Muslims?
This is not to argue for one moment that government policy should be made dependent on the perceived threat that it could upset a few alienated urban youths. But perhaps it's time at least to confront an obvious truth: that actions in faraway places can produce reactions on streets at home.
And while we're confronting obvious truths, here's another one: there will be no end to terrorist attacks (President Obama admitted as much in his speech last night). The police and the security services will do everything they can to prevent them, and to keep tabs on people whom they regard as potential threats -- but let's be honest: there's no way they can monitor round-the-clock every single disaffected youth, whether Muslim or non-Muslim, who spends too many hours looking up "How to make a bomb" websites or sending blood-curdling text messages to his mates.
A final point about the way the Woolwich attack was reported, and the widespread publication of the image of one of the alleged attackers with blood on his hands. I don't believe it would have been right to suppress the images once they had become available -- newspapers and other mainstream media organisations simply look foolish if they self-censor material that can lawfully be published and which is already readily available elsewhere.
But if I'd been editing one of yesterday morning's newspapers, I wouldn't have put the picture on the front page - and I would have used as a headline not the threats of the attackers but the words of Ingrid Loyau-Kennett as she confronted them: "It is only you versus many people, you are going to lose ..."
On a day like last Wednesday, surely it's better to focus on the heroes rather than the villains.