A peer at school asked me this recently--I was surprised to find that I didn't have an immediate answer.
Argument that it isn't:
-It's just telling someone that something you do wasn't meant with homosexual intentions
-You aren't actually using it to insult or make fun of homosexuality
-Everyone says it
Argument that it is:
-By saying it, you are clearly stating that homosexuality must be completely separate from other interactions
-You make people who are gay feel uncomfortable when everything you say is followed by it
-It has a negative connotation.
So is it or isn't it? I'm not sure I can give a direct answer, but here are some thoughts:
I think it's really interesting that especially for guys, basically any show of emotion warns that you could be homosexual. Says something about our society, doesn't it, that whenever a guy says or does something with feeling or emotion, it is likely that he's gay? Gee, that makes sense, especially because apparently girls like sensitive guys...
I would say that one shouldn't say it--there really isn't any reason too. If you are doing something that actually needs it (like making out with some other guy), then maybe you should consider your own sexuality. At any rate, I just feel like it promotes a negative environment. Guys need to man up and show emotion without being ashamed. Which sounds oxymoronic. But you know it's true.
So my consensus is: don't say it. Tell me what you think though--post a comment!