This has been my position since around the time when same sex marriage was being fought in the courts. Interestingly, a family member who is super conservative and religious came up with this same idea back then, and I was on board. (Her reasoning was that she wasn't against gay people having the same rights but that marriage is a "holy" bond between a man and a woman 🙄)

I've found that it's a way to get conservatives/religious folks onboard with same-sex marriage if their issue is the word "marriage" and ensuring its sanctity (cue eye-roll). It simultaneously outs the bigots because they can't hide behind religious BS, and they show their hand. Back in the '00s and early '10s, I would use it as a litmus test of which Republicans in my life I would continue to associate with.