Confusing a Girl

Miriam, telling me a joke: I know how to confuse a girl.
Me: Huh?
Miriam: Purple.
Me: Huh?
Miriam: See, you're confused!
Me: Why did you say, "girl"?
Miriam: Because that's the way I heard it.
Me: But it doesn't matter.  If you said that to a boy, he'd be confused, too.  If you specify that it's a girl when being a girl doesn't really matter, you're saying that girls are not as smart as boys.
Miriam, indignant:  That is NOT true! I'm never telling that joke again!!
Me, to myself: Thaaaaaat's right.