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.