You're not going to change the topic by saying "if a Christian has sinned once, it means they have no claim to recover their faith and abide by it fully." Two wrongs don't make a right. The warnings of Jude 1 are not ambiguous or unclear. They state clearly and emphatically that to assist in the moral destruction of an entire culture is banishment to Hell forever. Not mere pergatory until one has atoned. Perhaps Davis won't immediately enter the gates of Heaven, but she never would if she assisted a homosexual takeover akin to Sodom. She could hang it up and go straight to hell after that.
The reason the punishment is so severe in Jude 1 regarding homosexual depravity becoming mainstreamed (you know, like by calling two dudes "married"), is that that act doesn't just affect a handful of people at most as like with Davis' whatever marriage situation. It's that it teaches new generations of children "this is OK".
And over a relatively short time, there would be no soul left in that town, metropolis or even country or region who would consider the depravity a sin at all. It would simply be normal; as it was in Ancient Greece for older men to take boys as young as 6 years old away from their mothers so that they could sodomize them as they pleased. Women then hardly batted an eyelash when the pervert came to her door insisting she surrender her son to him. Indeed they had normalized it to such an extent that it was seen more like an apprenticeship "with benefits" for the boy. Often the older men were soldiers and if they had rank, a mother was proud her son was taken by him to be sodomized and otherwise "trained up" for a career.
So, you see, normalizing something depraved doesn't even give a whit of a chance of even recognizing the sin, much less overcoming it on a spiritual path. So while Kim Davis' divorce might be seen with scorn and disdain, affecting a small circle of people, we still regard divorce as "something unsavory, not to be striven for or cherished". On the other hand, your ilk wants to FORCE Christians to CELEBRATE "gay marriage" and all the other LGBT bullcrap, so the kiddies will all learn over the next 60 years or so that "depraved sex and sexuality is normal, OK, to be celebrated and cherished". And THAT is why Jude 1 speaks of normalizing homosexuality as such a grave, grave sin.