I think this has to do with whether biblical laws should apply to non-Christians or notwhether biblical laws should apply to non-Christians or not.
1 Corinthians 5:12-13 (ESV)
12 For what have I to do with judging outsiders? Is it not those inside the church whom you are to judge? 13 God judges those outside. "Purge the evil person from among you."
So, we should not seek to judge outsiders. Not even by democratically passing laws that aren't meaningful to non-believers.
However, we should seek the good of our country.
Jeremiah 29:7 (ESV)
But seek the welfare of the city where I have sent you into exile, and pray to the LORD on its behalf, for in its welfare you will find your welfare.
So it comes down to a personal interpretation of which biblical laws are good for the country as a whole, and which are just for the edification of Christians.
I think it makes sense to democratically uphold Christian morals as long as we have them. But once they're lost, there's not much sense to try and bring them back. In the process we'd judge a million people that don't believe in Christ either way and are not saved no matter what laws they have.
Still, we should democratically seek the good of our country. So the questions for each individual matter are,
- What effect would this have on the country as a whole?
- Would we be judging non-believers? How much?
A very important point to remember in our actions is this:
Ephesians 6:12 (NLT)
For we are not fighting against flesh-and-blood enemies, but against evil rulers and authorities of the unseen world, against mighty powers in this dark world, and against evil spirits in the heavenly places.
We are not to fight against other people, but the forces that keep them separated from God. God is our father, and theirs too -- they just don't know it. So our main objective should be to bring these people to God rather than pass judgement on their lifestyle. As @Flimzy put it, it's far more effective to love our gay friends than it is to pass laws about them.