If your only idea of what polyamory is like comes from abusive and patriarchal religious groups then I’m sorry to say you don’t know enough about the topic for your opinion to be worth anything.
Sure, John the Mormon who views women as incubators and rapes his wives and kids is terrible. Why should I be banned from marrying multiple people because of him, though?
None of the problems we have with John the Mormon are actually a result of him having multiple wives. They’re all things that are already bad or illegal independently, like child sexual abuse. They are also things that you can easily do polyamory without.
The argument here makes as much sense as banning all sex and relationships because abusive partners and rapists exist.
I don’t think Marisa the Liberal Bisexual who understands consent and doesn’t abuse kids is going to do polygamy the same way as John the Mormon.
if anything, having all those marriages be legal will make it harder for John the Mormon to abuse women because they will then be afforded legal protection such as divorce and family services. Fundamentalist Mormon enclaves practice their abusive form of polygamy in the way they do precisely because it’s not legal to marry more than once - so all those other women and children outside of the one legal marriage are at his absolute mercy and have no legal recourse against him. They don’t properly exist to even protect.
No it won’t stop all abuse, just like no-fault divorce hasn’t, but it’s made a very very large difference that shouldn’t be ignored.
So yes. I’m even aromantic and give no personal shits about marriage, but any adult should be able to marry whoever they want whenever they want, why would I even care? I only care enough to type this out because changing this little law would materially help vulnerable people, whether they’re a queer polyam qpr trying to survive capitalism or a young ex-mormon trying to keep her kids, I want more of a fair shake for the helpless. You must legally exist to be an entity worth protecting.