Under your logic, an unmarried heterosexual couple could be arrested for for fornication because their behavior promotes the spread of STDs. It has the potential for impact on third parties
Under your logic, adultery can be prosecuted, because it undermines marriage generally, exposes the innocent spouses affected to STDs and undermines the welfare of any children to the marriage.
Under your logic, sodomy could be prosecuted because it promotes the spread of HIV. Something that could affect third parties.
No, I said it's a privacy issue because it doesn't involve a third party, outside your bedroom. If it doesn't involve me or anyone else outside your bedroom, what goes on inside your bedroom between consenting adults is your personal, private business.
Once we clear up your misunderstanding of what I actually said, the rest of your post pretty much falls apart on its own.