Mousethief you seem to be saying(correct me if i'm wrong), that homos are no more promiscuous than heteros?

No, I am not. That's what you think I'm saying because that's the only claim you have an answer to. Allowing gays to marry is NOT going to make them any more promiscuous, and arguably will make them less so. Hence the level of "health" harm is at least a wash. Hence there is no good reason to deny them this right.