There's a bit of a difference in that one in every four women actually will be raped in their life, and a sizeable percent of those getting those threats already have been.
Yes, men are raped too. About 91% of rape cases are male->female, 8% male->male, 0.8% female->female, and 0.2% female->male. Men are virtually always the perpetrator, but even when the victim is male (not nearly as common, but still way more common than we as a society should accept), the perpetrator is still overwhelmingly likely to be male.
(and if the excuse for the stats is "men aren't as likely to report being raped by a woman because of shame"... so is there no shame for a guy to report being sodomized against his will by a man?)
The basic point is: when you're threatening a violent crime against a person who may well have been a victim of such, and even if they haven't, very likely has friends who have and is more than aware of their vulnerability in this regard, that's taking it to a whole different level.