“Hi, I’m Sarah Crank. Today’s my 14th birthday, and it would be the best birthday present ever if you would vote ‘no’ on gay interracial marriage. I really feel bad for the kids who have two parents of the same gender different skin color. Even though some kids think it’s fine, they have no idea what kind of wonderful experiences they miss out on. I don't want more kids to get confused about what's right and okay. I really don't want to grow up in a world where marriage isn't such a special thing anymore."
I don't know the reasoning behind this girl's and her family's opposition to gay marriage. However, I want to maintain that - from a Christian point of view - it is unfair to suggest that opposition to interracial marriage is the same as opposition to gay marriage. While opposition to interracial marriage in general cannot be backed up biblically, opposition to gay marriage is actually the default Christian position (look at the biblical evidence). Thus, it is simply not accurate to equate these two issues when it comes to a Christian's view on gay marriage.
Folks opposed to interracial marriage used Biblical citations all the time, and they even were implicitly prominent in Loving v. Virginia. Christians have no problem civilly recognizing marriages the Bible explicitly prohibits, such as among believers and non-believers, ostensibly on the grounds that it's civil and not religious marriage, and that religious liberty dictates that the government not make calls on scriptural interpretations like this. In fact, I've never met a Christian who is bothered by this holding, and I've asked. But gay marriage? Apparently that's different.
Of course it's not appropriate to equate the two. They are not the same thing, but the analogies are strong enough to show an obvious dissonance between conservative Christian's treatment of other types of religiously "questionable" marriages and the gays'. It all seems like weak special pleading to me.
The mere fact that there are people who try to find biblical reasons to oppose interracial marriage does not mean these reasons are legitimate. Indeed, there is no biblical passage that generally forbids interracial marriage. Rather, it appears that these passages opponents of interracial marriage so frequently cite condemn marriage between Jews and non-Jews or Christians and those who do not believe; it is the faith, not the race of people which matters here. So in order to come up with a biblical explanation against interracial marriage one has to do a lot of spinning.
On the other hand, you find passages both in the OT and the NT which literally and unequivocally condemn sexual intercourse between people of the same sex, which has led me to say that opposition to gay marriage is the "default Christian position". Only if one openly ignores these passages one can claim gay marriage is ok from a biblical perspective - but that puts you in a very weak position if you want to base your argument on the Bible; there are simply no passages in the Bible which can be interpreted as pro gay marriage.
Regarding the second point you made, yes, you are right. The Bible warns Christians to enter a (love) relationship with non-believers. But even if a marriage between a believer and non-believer is wrong from a Christian perspective, there is no realistic way this can be prevented because such marriages have existed legally for thousands of years already. Changing this is simply not feasible, unless you want to "privatize" marriage, an idea I could theoretically support. But does the fact that a non-biblical form of marriage already is place mean Christians should support all other non-biblical forms of marriage in consequence? I don't think so.
