Again, no one was denied a marriage license based on the color of their skin. The SC still found the Virginia law violated due process rights.
The right to marry someone you do not love is of little use. In fact, I would say the ban on same sex marriage is more of a fundamental denial of the right to marry than bans on interracial marriage. Even if one falls in love with someone of a different race it is not likely that one could only find love with a person of another race. A homosexual will not have the same sort of bond with a person of another sex. That bond is key to some of the most important benefits of marriage, e.g., power of attorney if you are incapacitated.
You have evaded and ignored the questions that put the lie to your slippery slope argument. Why haven't laws prohibiting bestiality been overturned? Why haven't laws concerning sex with minors been overturned, but have become more restrictive? The reason is clear, because those acts are not consentual. Unconsentual sex and marriage may be prohibited because the state has a valid interest in ensuring that the rights of indivdiuals are not violated. Society acceptance of homosexuality has increased dramatically while at the same time acceptance of these acts has declined. There is, absolutely, no reason to believe allowing gay marriage would lead to acceptance of these things, which are not at all connected.
Also, there are no marriage restrictions for people who share other unusual sexual preferences. Swingers, SM freaks, deviants who don't like oral, anything and everything is allowed in consentual marriages.
Your fear is unfounded and as far as I can tell, it hasn't even been offered as an argument in any of the challenges to gay marriage bans. Why, because it makes clear homosexual sex is being singled out for special condemnation, which would only weaken the position of one trying to defend the marriage bans.
A federal judge will soon rule on whether Prop 8 violates the US Consitution. I am not sure the time is right for this, but I think it's quite likely that the 9th circuit will overturn bans on gay marriage.
There is also an ongoing challenge to section 3 of DOMA which drastically changed how the federal government recognizes marriage and for the first time set federal guidelines. I really don't see how that will withstand a court challenge. Even the conservatives should vote against it as Congress has no power to encourage or discourage marriage. But I am sure Scalia will find some bullshit to justify his partisan vote.