I don't think calling a straight man a twinkie is homophobic. But I also don't think it's acceptable because it's certainly a negative attitude towards homosexuality.
That said, all words are just that. The intent is key. Calling a mate a twinkie or a Mediterranean_Descendant bastard (word filter alert) in jest is perfectly fine. I do think sometimes the reactions to things that are said are a bit over the top. That AFL dude is a perfect example. He's out of a job for saying a bloke looked like a twinkie. Ok, fine, bad choice of words. But Andrew Strauss says of Kevin Pietersen "the guys an absolute merkin" on live TV. And not being AFL, it actually had an international broadcast. Yet barely anyone said boo about Strauss....