I found it funny.
I don't agree with him of course, but I still found it funny. The idea that women can escape any kind of threat by just hiding in the toilets is frankly, ludicrous. Any determined man wouldn't be stopped from entering - the 'ladies' sign isn't some kind of impenetrable force field.
The joke kind of reminds me of the Mrs Doubtfire scene when Robin Williams keeps swapping personas/outfits and gets mixed up as he gets more drunk. Sally Field laughs and says, "You're going into the men's room", and he says oh yes, I need new glasses. Wouldn't happen now, people daren't make a comment about where they feel more 'comfortable'.
The part of the joke he conveniently missed out is that now no one can even question why a man is entering the ladies' loos. I saw it once with a very drunk man in a pub. I genuinely think/thought he was just confused and a bit lost looking for the men's, but swaying outside the ladies', peering at the sign. I just said, oh, the men's is that way.
He turned and yelled at me FUCK OFF I IDENTIFY AS A WOMAN and stumbled in.