When I was in high school (in ancient times) our principal ordered all the boys to line up and paraded them through the girls’ bathroom so they could see how clean it was in comparison to theirs. If men’s’ rooms are that bad, I don’t blame anyone for wanting to use the women’s’ restroom instead.
I don’t know what people expect trans women to be doing in the bathroom that’s any different from anyone else. From what my husband tells me, men stand next to each other at the urinal and pretend the other person doesn’t exist. The social norms about personal space are the same. I’m sure a lot of people made the same complaints when restrooms were desegregated. They’re no more valid now than they were then.