Members of the lavender lobby like to point to the alleged parallels between statutes against gay marriage and those against mixed race marriage. Historically, the comparison fails. With a very small number of exceptions (so minor that hardly anyone even knows what they are), marriage has always and everywhere been a man-woman thing. Anti-black racism, on the other hand, was invented to justify black slavery in the New World. The invention was fairly recent, as historical things go, and probably reflected a subconsciously guilty conscience on the part of the inventors.