This is an ambitious take. There are so many cogent counterarguments here that it's tough to choose one, but consider this:
The fundamental core of the American societal experiment was a separation from an overbearing authority in the pursuit of individual liberties. It seems clear to me that freedom to marry who you want, where you want, and how you want would be pursuant to that eidolon. Now, you don't have to agree with that core tenet, but on an empirical level _that rejection_ would be degeneration: a fall from first principals (which might not be a bad thing depending on your normative frameworks - I'm inferring that you're not a fan though).
What I find interesting is that it seems, in the US, that the same people who reject the control of the government in things like guns, taxes, state-level decisions, etc., are the same that want to impose control of the government on things like marriage, sex, etc.
IMO It's because - going back as far as the constitutional convention - political ideology in America has largely comprised of aesthetic movements that wear the shells of theory and policy for memetic power.
I had a religious studies professor make a - reasonably evidenced - claim that the whole 'seperation of church and state' stuff during the revolution was widely understood to basically be lip service. The vast majority of Americans were under the impression that they were starting a Christian country with a Christian government. That same professor made the - less evidenced - conclusion that the implicit divide between that expectation and the legal reality has underscored a considerable portion of American political turmoil to date.
It makes sense since separation of church and state isn't in the constitution. The establishment clause was to avoid the establishment of a federal religion. Many states had their own state religions until the 1800s. The founders did base the idea of Natural rights based on a creator. Most were either deists or christians. It's hard to come to the idea of inalienable rights without believing in a creator.
State or religious marriage is a relationship with an authority. You can swear eternal loyalty to anyone and however many people you want to without any of that.
Primarily state marriage is about sharing privileges and duties before the law.
While this is true on a purely de jure interpretation of the dynamics at play, a more clear-cut example - like same-sex marriage - makes it clear that the "right to marriage" includes not only the right to life-scale commitment to a person(s) but also the right to have that commitment recognized by the state. Insofar that marriage as a legal construct carries additional privileges alongside the simple recognition, which it does, the "right" to marriage must also include the "right" to access the consequent privileges or you have a structure of authority stripping those privileges by omission.
Why does it bother you that people can live their life in a way that makes them happy and fulfills them, but it in no way infringes on how you should live your life? They'd probably be happy for you that found your one soul mate; you could be happy for them too!
Edit: didn't mean to accuse you of anything, but to offer a different perspective to how the situation could be viewed
I don't think this will cause a degeneration of society. If anything, the American export of "everything is us versus them" tribal mentality to politics and society is much worse. Granted, some of that always existed but I feel like it was waning until social media and exposure to American politics started reviving it. Please don't let it influence your daily life like that
They are there, but, as posted by others here, mostly care about gun ownership and covid restrictions and their own speech, but not about people getting literally tread on by police or humane treatment of asylum seekers, etc.
You should have thought of that when you banned them all for saying that the sky is blue and water is wet.
The "Don't tread on me" side of the population - I don't think "the right" is the correct term here - tends to be want left alone by overreaching governmental busybodies. They also tend to be more on the traditional side of societal norms - again not something which is limited to "the right", there are plenty of traditional left-wing thinkers who did not like the "free love" movement of the 60's and don't like it still - so are not wont to go for polyamory unless they happen to be Mormons and talk about polygyny.
The fundamental core of the American societal experiment was a separation from an overbearing authority in the pursuit of individual liberties. It seems clear to me that freedom to marry who you want, where you want, and how you want would be pursuant to that eidolon. Now, you don't have to agree with that core tenet, but on an empirical level _that rejection_ would be degeneration: a fall from first principals (which might not be a bad thing depending on your normative frameworks - I'm inferring that you're not a fan though).