Amen to that.
But in other cases of legal prohibition of sex-related matters - statutory rape, for example - equal protection arguments will usually carry the day. And unless you get into playing percentages, on AIDS for example, I don't think you're going to see a compelling argument justifying the distinction in this case. And the law is not based on percentages.
I think that with this court that the argument does not need to be particularly compelling, just sufficient to justify application of their personal views. And with the underlying health concerns of AIDS, it does give the state the ability to state an interest in the matter. Like I said, I would tend to disagree with the statute, but I've learned over the years that SCOTUS is actually the most political branch of the federal government, and they tend to make up their minds and then go fishing for a rationalization for that decision - a classic example being the recent upholding of notification of sex offenders, where someone convicted of the crime prior to the enactment of the law is still required to register, which IMO is a clear violation of the Constitutional prohibition against ex post facto laws - which the court sidestepped by decreeing that the notification was not a punishment.