To do so in broad daylight and in the middle of the road, while asking passers-by to take pictures, simply beggars belief.
Few can understand how the British jihadists Michael Adebolajo and Michael Adebowale could be filled with such hate.
I'm ashamed to say I can. For I was similar to them once.
I spent 13 years inside Hizb ut-Tahrir (HT), the global Islamist organisation that first spawned al-Muhajiroun, the banned Islamist terrorist organisation founded by Omar Bakri Muhammad and Anjem Choudary.
Bakri and Choudary both knew Adebolajo, a 28-year-old who was raised as a Christian. Like Adebolajo, I was raised in Essex in an educated, middle-class and well integrated family.
Again, like Adebolajo, I went on to further education. He dropped out, while I gained a law and Arabic degree from The School of African and Oriental Studies and a Masters in political theory from the London School of Economics.
(The belief that all radicalised young Muslims must lack jobs or are socially awkward loners is a dangerous misconception. I did not lack career opportunities, nor did I lack friends or girlfriends.)
And I, too, was caught up in the aftermath of a Jihadist street murder in which a man was killed with a machete. It was 1995 and I was president of the Student Union at Newham College in East Ham. The union was nothing but a front for HT. We siphoned off money to our cause, giving lectures and preaching anywhere and everywhere - the street, the yard and the canteen, where I would stand on the tables and spout hate.