The point is that the threat cannot be real (to the class as a whole). Indeed, it is hard to consider it real to an individual, unless you think there are gangs of women going around beating up men just for being men.

Surely you can see the distinction between a real and possible threat, that might genuinely put fear into the object class, and words that can never be actioned? "Kill all men" might as well say "beware of the vicious rabbit"