So a when we were talking about double standards and sexism in english class, a guy joked "A lock that is unlocked by many keys is a bad lock, and a key that unlocks many locks is a master key" (yeah that's an metaphor for sex in case you didn't notice) . I said to him "A pencil sharpener that sharpens many pencils is a good sharpener, but a pencil that is sharpened by many wont be a good pencil for long"*.
*I got this from someone here who responded to the same "lock and key" thing with that comeback. Sorry, I forgot who it was... I think it was in the "Dumbest protest signs" or "dumbest political cartoons" or "Things people say on facebook rehashed" threads...