Short answer: Chris' homophobia (or not as the case may be) is irrelevant. The language he uses is homophobic.
Longer answer:
Every time someone uses "gay" to describe something that sucks/isn't cool/whatever it cross-reinforces the belief that if something that is crap is gay, conversely anything that is gay is crap. I accept that when someone says "that music is so gay" they don't actually mean that it has a homosexual orientation, and they're expressing their dislike. But there is no way on earth that Chris could get away with saying "that's so ni$$er" - it just wouldn't be permitted by listeners at large, and rightly so. I know that there is currently no group that uses "ni$$er" in a colloquial way to describe "lamness/crapness" of things, but the point stands for comparison.
In fact, to take the example further, Chris wouldn't be able to say "that's so ni$$er" even if he was talking about Black/Afro-Carribean music because simply the word itself is offensive, and from that perspective so should gay be viewed. I'm not gonna get into a debate about Black people saying "ni$$er" - that's a genuinely different debate about reclaiming the words - but it seems to me that the outrage expressed by the British public at the treatment of Shilpa Shetty in BB earlier this year, which used far milder language than that, would support my view.
Finally, even though (as I believe) Chris is not homophobic, and that his use of "gay" is meant in the non-sexual-but-still-derogatory way, I think it's wrong. People in the public eye have a duty to try and shape the culture of acceptability - let's not forget that as a BBC DJ Chris is paid by taxpayer's money! That includes all the gay (and other) people who find his continued use of the word offensive. He has a duty in which he is currently derelict.
E
You put forward a good point, ellipse, however - i'n not sure I completly agree with you.
Firstly, could it not be argued that Chris, as he is being payed by the taxpayer, should reflect the language, and behaviour of his demographic that he is aiming his show at? There has to be a line drawn at some point where people need to say "enough is enough - we can't go on being offended at everything and anything."
Can someone post what it is that Chris has said by the way, coz I still aint sure of the context of this particular "offence".