On the one hand, I've read arguments that the bible doesn't condemn homosexual acts and they've always seemed a bit of a stretch to me, although I haven't delved into them too meticulously.
On the other hand, it's true that the bible in one passage or another condemns all kinds of things that Xians who claim to be strict in their adherence just flat-out ignore, and rightly so. The selective reading is just a grasp at permitting themselves a moral or rational homophobia, just as it was in the past to justify racism. If you want to use the bible as a rationale for homophobia, come see me when you endorse and live by all its other harebrained passages. It would demonstrate unusual integrity while establishing your credentials as a complete nutter.
Regarding the comment that gay marriage proponents are trying to force churches to change their policy via laws, I've never heard of that. It does sound an awful lot like what right-wing moralists would LIKE you to believe is happening, as part of their general sky-is-falling campaign, but I doubt it's actually so. For instance, I would guess that churches (here in the US anyway) remain free not to marry inter-racial couples if they so choose. What's at issue is only what the state would recognize. So don't be conned on that score.
I'd also be curious to hear what the "social and economic ramifications" of gay marriage, mentioned in passing earlier in the thread, would be.
Finally, here's a timely quote from the prime minister of Spain, that bastion of Catholicism which just legalized gay marriage:
"We are enlarging the opportunity for happiness to our neighbors, our co-workers, our friends and, our families: at the same time we are making a more decent society, because a decent society is one that does not humiliate its members.. . .
"Today, the Spanish society answers to a group of people who during many years have been humiliated, whose rights have been ignored, whose dignity has been offended, their identity denied, and their liberty oppressed. Today the Spanish society grants them the respect they deserve, recognizes their rights, restores their dignity, affirms their identity, and restores their liberty.
"It is true that they are only a minority, but their triumph is everyone's triumph. It is also the triumph of those who oppose this law, even though they do not know this yet: because it is the triumph of Liberty. Their victory makes all of us (even those who oppose the law) better people, it makes our society better."