rsjm brought up a sermon on 1st Corinthians, where Paul is telling the Corinthian church to behave.
Paul says, "Just because society thinks it's ok, doesn't mean God does". I accept that as a fundamental of Christian belief, and don't see any problem with a Christian chosing to live their life that way.
Paul says that God's rules are for God's people. That's a very Judaic way of thinking, too, and an area where Christianity changed from Judaism. Jews believe the rules in the Torah are for them, and they're the only people who should live by them, and too bad about those other folks.
Christianity, OTOH, expects *everyone* to live by their rules, and some are willing to impose those by force and law.
And that's where Christianity and I break. They (in the general theological sense) accept their morality as the only morality, and no one else is living a moral life but them. And, especially recently, power-holding Christans are willing to enfoce their morality through the law. This, in my mind, risks puts things on par with the thecracies of the Middle East, and other places where religion is state-enforced. Especially in America, no one religion should have the right to enforce its beliefs on the populace.
I think until Christianity as a whole begins to understand that people of other faiths can be moral beings, and that morality is much more about how we treat the people around us, and less about arbitrary rules, there will always be a cultural rift between Christians, and non-Christans.