He might well be a dick. He's a celebrity comedian. Though the fact that some anonymous poster says he is on the internet is not exactly proof.
I agree that he shouldn't have been in women's loos, though he was dressed as a woman (when he went in) and can see that I probably wouldn't have fancied my chances going into a men's public toilets dressed as a woman in Islington in 1980-something. Nothing in what he wrote suggested he did it in order to 'validate himself', as JigglyTuff put it - that seems to come from your imagination. It comes straight after a section where he talks about his fear, so that is at least as likely a reason for his choosing not to brave Islington men back in 1980-something. Islington then, by the way, was a long, long way from the posh, gentrified area it now is - it wasn't multi-million pound houses and lattes, it was extremely down at heel and notorious for its council estates and crime.
And the whole issue of which sex toilets you use just wasn't something I ever remember people discussing until about 2 years ago. I guess he put his own safety before worrying if he'd frighten anyone else in the toilets at the time, but to be fair he makes it very clear he was desperately hoping there'd be no-one in there, he wasn't hoping to intimidate anyone. I daresay these days he'd think more about which toilets to use, because it's something that's talked more about and no, for the record, I have no idea whether he is in favour of using female toilets now.
Again, I just find it odd that this piece, exploring an interview published last year, is being discussed on the very day Izzard takes over from Christine Shawcroft, who is indisputably guilty of far, far worse.