@ValK I just knew that you were going to come up with HIV and the like.
HIV is extremely treatable these days, and people live normal lives with the virus. So why is it worse than chlamydia, gonorrhoea, herpes, and syphilis, which are diseases that can arise from promiscuity in both gay and straight populations? How does this affect the whole of society? What is the cost of PREP to the NHS as compared to the cost of treating other lifestyle diseases like obesity-induced diabetes, cancer caused by smoking/drinking, major injuries caused by drunkenness? And why are they not just as bad?
Then there is the question of what you're going to do about making homosexuality illegal. Are you going to put people caught having consensual gay sex in jail? Are you going to do the same to lesbians, even though their health outcomes are not in the same league? Are you going to extend the illegality to sexual relationships between people who are not married, and impose on them the same punishment? That would be 'equality', but that would make us as bad as countries like Iran and the like. Is that what you want to see?
You offer very simple thoughts, but you don't appear to ask yourself what the consequences might be of having what is in effect a theocracy. Which is odd, because all you have to do is look at what's happening in countries all around the world. Regimes founded on religion are oppressive and undemocratic.
On marriage, why is a marriage between a gay couple not the same as a marriage between a straight couple? Both can have children and raise them by a variety or routes. I agree that surrogacy is problematic, but other routes such as adoption are not. Why do you want to deny gay couples something straight people take for granted?
In the post I originally responded to, you did not differentiate in any way between incest and homosexuality in terms of their negative impact on society. Hence my assumption that you think they are equally bad.