I was a same-sex marriage supporter long before it was cool, I have gay friends. But I until recently I used to say "that's gay" when I meant "that's corny" or "that's cheesy." A lot. My 20-something gay friends might not give a fuck, but your "It Gets Better" Project made me think about how hearing something that could pretty tough on a kid who was just coming to terms with his sexual identity.
The funny thing is that "that's gay" is rarely used to disparage things that are generally fancied by gay people. "You like Lady Gaga? That's gay." No, it's more like, "You like Billy Joel? That's gay." And then it suddenly hit me: the shit that my friends and I called "gay" was all the stuff that the Mormon kids at my high school liked, those I'm-hot-and-I-play-football/cheerleader-but-I-don't-drink-and-any-music-heavier-than-the-Beach Boys-scares-me types.
So I've decided to start saying "that's Mormon" instead of "that's gay" and encouraging my friends to do the same. It's more accurate and plus it gives shit to a group of people who have extremely backward views about homosexuality. Maybe you can encourage your readers to do the same.
Latter Day Sinner
Hmm...
A Mormon kid in high school would wind up hearing "That's Mormon" ten thousand times a day if your proposal caught on, LDS, while a Mormon adult would rarely if ever hear the expression. (I'm a gay adult and I can't remember the last time I heard anyone besides my husband dismiss something lame with "That's gay.")
Mormon kids, of course, have the family support so many gay kids lack and they're not committing suicide at greater rates. So I suppose "That's Mormon," if it caught on, would do less harm to Mormon kids than "That's gay" does to gay kids. (And you know how Christians get off on feeling persecuted.) But are Mormon kids to blame for their backward views about homosexuality? They've got those views because their dipshit parents and hateful religious "leaders" pounded them into their heads. So it seems a bit, ayedunno, unfair that Mormon kids, and not Mormon grownups, would be exposed to "That's Mormon" on a daily basis.
However...
If "That's Mormon" were to replace "That's gay" as slang for lame/stupid/embarrassing, teachers and school administrators wouldn't hesitate to confront kids who used the expression. The exact same school officials who turn a blind eye to casual-but-harmful expressions of anti-gay bigotry—because those officials are either anti-gay bigots themselves or they're terrified that confronting homophobia will lead to accusations of "promoting homosexuality" from bigoted parents—would, without a doubt, be vigilant when it came to confronting casual-but-comparatively-harmless expression of religious bigotry.
So I will allow it. (And in the interest of full disclosure: I like Billy Joel.)