It is promiscuity and failure to practice "safe sex" that leads to an increase in STDs.

And what leads to promiscuity? Well, many things do. One thing that appears fairly obvious is that the average man is more inclined toward being promiscuous (having casual sex) than the average woman is...given that women are on average more inclined to look for an emotionally satisfying relationship that provides some longevity and security. (Yes, I realize there are individual exceptions to that, but I'm talking about averages here.)

Therefore, it doesn't surprise me that male homosexuals are more inclined to have many different partners than, for instance, lesbians are...and that male homosexuals are therefore (on average) at greater risk of acquiring and spreading STDs. Also...how many of them bother to practice safe sex (using a condom) when they obviously aren't worried about getting their male partners pregnant?

I don't feel that this has any particular bearing one way or the other on a debate about the merits of gay marriage. It does have bearing on a debate about public health issues, however.