Though it varies widely by degree, I don't think it's ever been ok for a woman to act like a man. Sure, kids get away with a pretty much a pass for being a "tomboy," but manly women are assumed to be lesbians just as surely as effeminite men are assumed to be gay.
And yes, it's also different by a wide degree that lesbians are ok with men, while queers are threatening to them. Men are idiots, generally speaking. But the fact remains that men can never fear being a lesbian, and are too often fearful of their own homosexual urges.
I maintain, however, it's only a difference by degree. People acting outside of their own gender norms has traditionally faced scorn whether they are male or female.
Yeah, the phrase, "That's so gay" is expressing a negative value judgment on effeninentism. Probably one that the person saying it doesn't even really feel about actual people ... but it's a value that's been out there in society, thankfully fading, but not quite gone.
Before anyone gets their secretly worn frilly panties in a bunch, why don't you check all the stock phrases you use for any anachronistic value judgments embedded in the English language. There might be more of them than you think.
Think of all the offense possible with the innocently-intended "Happy Jew Coon."
