I call BS. Yeah, it's annoying when someone gets offended on someone else's behalf. But that is not the only reason someone would get offended. Maybe they just think something's offensive. You're allowed to be offended by something even if it's not targeting you. Really.

And in that vein, the notion that "being gay isn't a choice and isn't anyone's fault" is, actually, pretty offensive. It implies that it's something that blamed needs to be placed for.