Well, after a brief Google search, here are just a sampling of the Biblical passages that were used to condemn interracial marriage:
Leviticus 20:24 says:
Exodus 33:16:
Joshua 23:12-13:
Deuteronomy 7:3:
2 Corinthians 6:14:
Acts 17:24-26:
I think it's fair to say that these passages are at least as clearly anti-interracial marriage as the usual suspect passages are anti-gay marriage (or, more generally, anti-homosexuality). In fact, just looking up those Biblical passages somehow made the interracial marriage analogy even more accurate than I had already thought it was. The thing that bothers me the most is that people don't even seem to care to back up their statements. It only took me about 10 minutes of research to find evidence against your assertion that there was no reference to interracial marriage in religious texts, and yet you use that assertion as a foundation of your argument.
It seems unbelievable now that these passages could have been used to condemn interracial marriage as sinful and contradictory to God's will, but the fact is that people genuinely believed that that was the truth, and then they somehow convinced themselves it wasn't discriminatory because it was God's word. It's not like I'm not making it up. People really believed that the races shouldn't mix, and those are some of the Biblical passages that they construed to support their view, a view which, in my opinion, was almost certainly rooted in some deeper level of discomfort with the idea and with breaking the status quo.
I mean seriously, how much more valid can this analogy get? It's so similar I can hardly believe anyone would try to deny it at this point. If people want to simply ignore the concept of context and accept these outdated interpretations about what marriage is and isn't, then that's fine, they can live in their fantasy world where Biblical interpretations have never evolved at any point in history. But don't dare try paint over history with absurd illusions that this is somehow completely different from the shamefully late cultural, moral and legal awakening that gave interracial couples the right to marry.