I'm not a fan of "gay" being used in a derogatory fashion. Both when it's used to demean other people and when it's used to express dissatisfaction with some thing or concept or... whatever. This is not a secret, I've railed against it any number of times.
But why? Why isn't it okay to say a Team Fortress 2 map is gay? Or the pen that keeps running out is gay? Or paying extra for pineapple on your pizza is gay?
Because every time you use it that way you're reinforcing the notion that "gay" is synonymous with "bad". And therefore being gay is bad.
You may not mean it in the sense of homosexuals being bad. It likely doesn't cross most people's minds at the time they utter it. It's become so ingrained in some people that they'll actually defend their usage of the word. They think it's been "reclaimed" or somehow repurposed to not refer to homosexuality anymore, despite the prominent usage in various advocacy groups and celebrations like the Gay and Lesbian Mardi Gras.