Izzard is a well known cross-dresser (let's leave whether he is a 'trannie', a 'transexual' 'non-binary' or whatever for now).
He was at a venue where everyone knew who he was, and in any case couldn't pass for a woman in a howling gale.
Had he used the Gents, his cover wasn't ever going to be blown, was it? This was a deliberate way to make some sort of point. not an awkward moment when someone trying to 'pass' has to decide between using the wrong loo and outing themselves.
I do have sympathy with transwomen who who are in that situation. Some are mentally fragile (not all, before I am pounced on) and would suffer if they had to 'expose' their real sex, however obvious it may be to everyone present. Spending ages on your make-up, choosing an outfit carefully, perfecting mannerisms etc then having to use the male loo can't be an easy situation. I get it. But that shouldn't be a problem for women to solve. The fact that a small number of people are in this position is unfortunate, but it is not my problem. It enrages me when people say ' if you don't like men in the Ladies, what would you do about it? Where do you think they should go?'
I have no real idea, but even if I had I have no power to put it into place. Why would I spend time and effort coming up with an answer to a difficult problem that is not of my making? It is a male problem - let men (or transwomen) solve it, or leave it to the politicians whose job it is to legislate, and who have think-tanks, access to experts and far more data at their disposal than I do.
If anyone wants to tell me that my attitude is 'unkind' or selfish, please think about whether you would feel the same if a man said similar. How many 'female problems' do most of them spend time solving (unless there is a monetary advantage or sales opportunity, that is)?