I started hearing this expressionfrom my son and my son’s friends starting in the 4th grade. Of course, I’d heard the expression before. My own family used to use the expression right to my face even after I’d come out to them.
But that was a while back and I’ve gotten married and had kids since then. I never hear it anymore from family or friends and I guess I’d hoped that this particularly hurtful expression had disappeared. But I just must be travelling in different social circles, because I’ve had to have this conversation, almost word-for-word with my son. In fact, I’ve had this conversation with my son’s friends. It’s pretty funny, because the open-mouthed goldfish reaction was identical to that shown in this public service announcement.
I think this expression is a social virus for a myriad of reasons. Each of us need to give this short and sweet speech to everyone infected.
Huck's House 
Maybe a more effective strategy would be to start using this phrase in a positive way. If you cook a really tasty meal, I could say, “Wow, this meal is so gay!” Or if I suggest we go out for ice cream after diner, you could say, “That’s a gay idea!” 🙂
That might just add to the existing confusion. This expression is fraught with enough subliminal meaning as it is, which is I think why my family would use it even when they knew I was gay. I could tell that they hadn’t thought about the expression and its meaning (or its hurtful effect on me). They had picked it up as hip slang and used it indiscriminately. But perhaps by using this expression in front of me, they were unconsciously expressing their confusion about my sexuality at the time, because now they never use the expression anymore. Maybe that’s because their tension about my sexuality has disappeared now that I’m married with children.