Tim Keller tackles the most common arguments in favor of loving gay relationships in the Christian context:
[W]hen I see people discarding their older beliefs that homosexuality is sinful after engaging with loving, wise, gay people, I’m inclined to agree that those earlier views were likely defective. In fact, they must have been essentially a form of bigotry. They could not have been based on theological or ethical principles, or on an understanding of historical biblical teaching. They must have been grounded instead on a stereotype of gay people as worse sinners than others (which is itself a shallow theology of sin). So I say good riddance to bigotry. However, the reality of bigotry cannot itself prove the Bible never forbids homosexuality. We have to look to the text to determine that.
I’d say a change of heart after getting to know gay people who don’t fit our previous bigoted stereotypes easily accounts for the biggest shift in cultural acceptance of homosexuality, especially within the western Christian church. That’s certainly what I’ve seen. Most people aren’t doing intense, sincere study of these things in pursuit of the truth, no matter how uncomfortable they may be with it. They’ve simply met some gay people they genuinely like, and they want their friends to be happy.
Keller is spot on: if all it took to change our minds was befriending gay people who don’t fit our preconceived notions of homosexuality, then we were bigots indeed.
The whole piece is worth a read.