Because men allow it.
You have women trying sticking a finger(s) in a man's ass and then try to call him gay in public to be ridiculed if she's mad. Men get judged for not being sexual with a woman in a certain way otherwise his sexuality comes into question, lol.
Not following your statement. Not challenging it though. I genuinely don't know what you mean. A woman can't finger a dude's ass if he didn't want that, and a man can't tell a woman not to do something sexual with another woman.
I just have run across so many women who claimed to be lesbian, but would flip and want to fukk me in my 20+ years of dealing with women. Everything from femme lesbians to butch lesbians that have come at my neck to women who never did anything with another woman suddenly wanting to bring another woman into the fold, that I realized that sexuality isn't a hard line for women like it is men. It's how they feel in that moment.
Stigmatized or not, I ain't never have these thoughts about another dude. I'm just not wired like that. And I constantly think about conflicting opinions on stuff.