Marriage is just a contract. Everyone should be able to enter into a contract with whoever they want. Forcing churches to have the ceremony, etc, is a different thing.
Any two people should be allowed to enter into a legal contract with one another.
Marriage is a personal covenant between two people and their preferred deity, sealed by an officiant of that religion under blessed/sanctified conditions (usually in/on a holy place, like a church or other sacred ground), ideally before friends and loved ones. It's not a transaction. Reducing it to that degrades and demeans the significance and sanctity of it.
What you're describing (reducing the concept of two humans joining together as one soul for life to a simple "contract") is called a "Civil Union," which is what the man-made paperwork minutia that accompanies every wedding (including marriage ceremonies) confers upon the couple. Atheists and other non-practicing people can seek out civil unions too. You can go to the local courthouse to get one. It's kinda cute (I've attended a few) -- they usually have a little room with some fake flowers, a little archway and podium, and a Justice of the Peace officiates and is usually grateful for chance to perform a
pleasant duty rather than the usual fare.
Fags and dykes already had access to that, since they mostly view it as transactional like you seem to. They just wanted to shit on religion as much as possible (since they already blaspheme by engaging in deviant sex acts) to piss people off.
If access to the legal protections and rights civil unions grant was all they wanted, it should have been sufficient. They could have their own ceremony under whatever auspices they want; if they can invent (or find) a religion with a deity willing to tolerate butt-bumming, more power to them. But forcing themselves into the sanctity of marriage (in the religious sense) was just another way to force themselves onto everyone else, much like pride month, pride parades, drag queens reading books to kids in libraries, etc., has been.
I'm not even religious and I understand this shit. It's not hard. "Gay marriage" has always been about debasing and contaminating sanctity, not "equal rights," which they already had.