The definitive answer to such a problem is spiritual. If nobody WANTS the “gay marriage” for whatever reason, then we won’t be plagued with it even though it remains possible in principle.
I don’t want abortion, either, but it’s been unsuccessfully challenged so often and been in place so long that it is considered ‘settled law’.
Despite that, there is a far more concerted effort to remove abortion than to remove same sex marriage. To be fair, same sex marriage has only been judicially imposed for about a year and a half now, so one wouldn’t expect that the opposition would gain their balance and begin a counter-offensive.