Smoking gun is "...a reference to an object or fact that serves as conclusive evidence of a crime or similar act."
I'm suggesting that these sort of attacks on men are extremely limited is enough evidence to suggest the perpetrator is likely to be sexist and/or a mysoginist, which is pretty much the definition of a smoking gun as illustrated.
Think about where the term literally stems from. A smoking gun may tell who did something and what he did. I have trouble imagining a gun (smoking or not) explain why he did it.
fact that serves as conclusive evidence of a crime or similar act...
The fact that I'm asserting is that men do not suffer these kinds of attacks suggest the individual was motivated by sexism. I can't say anymore other than to say that you are wrong. I don't think it means what you clearly think it means. Sorry, no snark intended.
I don't think that means what you think it means.