The idea that it would be more practical to arm every woman than to teach men about rape is depressing -- and it's insulting to men. It's an extreme manifestation of the classic "boys will be boys" mentality -- and everyone but the "boys" are responsible.
Threats like this are not harmless expressions of free speech. They're akin to hate speech and are maliciously intended to intimidate and silence. Messages like this don't make women feel safe. And that's the point, isn't it -- to make sure our gendered safety gap stays constant.