All sexual acts can potentially spread disease.
That's true, and I expected this response. I am personally opposed to laws regulating private, consentual behavior, but I can still imagine rational arguments for such regulations.
All promiscuous sex has much greater risks than monogomous sex. In fact it has probably lead to more deaths than all the known wars in history. (We worry about smallpox, but the great pox was syphilis, and was as deadly as aids is now.)
I'm not arguing in favor of laws, just arguing that there can be a rational basis for them. Sex certainly kills more people than guns.