It is certainly the case that in Romans, Paul makes statements that could be construed as dismissive of homosexuality. But he also makes statements condemning depictions of God and Jesus, fornication, gossip, disobedience to parents, etc, and says that all these things are worthy of death. He does not say that any are worse than others.

But in the very next chapter he repeatedly says that man is not to judge and that this is only God's duty, not man's.

Of course this was the same Paul who said that women should be silent in church and only raise questions at home and yet in other passages spoke with pride of women church workers and leaders.

So...it's probably best that The Bible not serve as the reason for secular law. We have separation of church and state and that's a good thing. People who are anti-gay marriage will have to find non-religious reasons to convince people.