(edit: apparently people are cool with this. That's weird. I'm not claiming the parent is untrue, it's just that you shouldn't talk smack about people in public without presenting evidence if you don't use your real name.)
From what does the supposed requirement to use one's real name derive?
The internet is protected from the forces that threaten physical forums where each voice is a real person. You cannot pay off the internet to talk nice about you, and you can't follow anon home and beat him up for speaking negatively. It sounds like Jurgen has accumulated some bad karma on the internet; this is not baseless accusation as much as it is keeping ourselves at a healthy level of skepticism regarding someone who has already lost our trust. The cowards with loud, strawman accusations are usually appropriately downvoted when their criticisms are out of place.
And btw, I think his sense of humour - and brilliance - comes across best in person. I recommend attending one of his talks or watch a video. But just do it once, otherwise you'll hear the same jokes again.