The world is full of people who use that excuse, or any of the "reasons" on this list, really, to insult other people.

Yeah, very good point. I think one of the worst part of gender-expectations is that it means that when people are insulting that way, they're supported by a great deal of popular opinion, in a way that they wouldn't be so much if they were cruel in a more individual way. It's seen as just a slightly harsher version of the norm, rather than an outlier. It's sucky.