Unintentional insults can be bad too! I'm still going to get a little bothered by people calling things "gay" even if they don't mean to be homophobic.
I'd personally say that calling something gay is inherantly homophobic. It's implying that being gay is a negative thing.
"Gay" is an interesting word in this regard due to it's dual (triple?) meaning.
First off, words evolve. The original meaning of a word can become irrelevant (gay doesn't mean happy anymore to most people). That the negative connotation of the word stemmed from homophobia is rather irrelevant, because in the end the speaker is just intending to say something's "bad." Thus I do not think it is
inherently homophobic when used in a negative context (though definitely could be, and probably most often is).
It certainly can fall under miscommunication though, which is a good enough reason to censor yourself from using it. The reason of course is due to it's dual meaning; an idiot, when hearing both definitions, can
equate them, and thus it's reasonable to think that a listener might misinterpret. If you call something you don't like "gay," the listener could reasonably think you're equating it to homosexuals.
Your intention might not be to insult, but that's why miscommunication is miscommunication. And of course, if the
listener can equate the two meanings, so can a
speaker, so using the word in the above fashion could very well be
intended to be insulting to homosexuals.
This will be a problem until the two meanings are completely decoupled. So yeah, I'd never say something is "gay" when I mean bad myself.