“Where does it stop?”
It doesn’t, which is precisely why conservatives adamantly defend traditional marriage.
Once you condone, legalize abhorrent behavior you can expect a fast track to debauchery.
Traditional marriage was destroyed when divorces were allowed, everything else has been a slippery slope since.
When “conservatives” defend marriage not just against same sex marriage, but against divorces, then I will know they’re serious about protecting traditional marriage.