All of the precedent on the issue of "marriage" was made with the understanding that marriage meant a union between a man and a woman. Both the majority and dissenting opinions in today's decision acknowledged this fact.
Loving v. Virginia was struck down because it sought to arbitrarily hinder this right. However, gay marriage is a very different issue, because it seeks to expand the right to more people.
Well, as the history of this country has been one of expanding the scope of rights to encompass more people, rather than one of limiting rights to only apply to folks that think and act like the majority, I'm for it. The only time we tried to limit rights with a Constitutional amendment (prohibition), things didn't go so well.
I would also take issue with your framing of this case. I view gender as just as arbitrary a hindrance as race, especially given that the "Biblical definition of marriage" also dictates things like how one should treat their sex slaves. It's also worth noting that it was religious conservatives that were also raging against the decision in Loving v. Virginia, because it violated "traditional" notions of marriage.
So, what's the difference between an "arbitrary hindrance" and an "expansion of rights"? Who gets to decide? Which one is allowed, in your view?
Loving v. Virginia was struck down because it sought to arbitrarily hinder this right. However, gay marriage is a very different issue, because it seeks to expand the right to more people.