[monktastic1]

To put it another way: suppose I ask someone "why did you forget my birthday but not his?" It's not that I want them to forget his, too (though that is one literal interpretation). It's to suggest that the answer isn't merely "I forget birthdays in general."

[mehrdadn]

That would be weird in this situation since "I mention every gender in general" would be quite a bizarre response (and behavior)... and arguably even more fuel for subsequently accuse the speaker of sexism if that's the intention.