Sharing a household with a genetically unrelated adult is one of the biggest risk factors for experiencing child abuse. This is well known and well supported by evolutionary psychology: https://en.wikipedia.org/wiki/Cinderella_effect
Therefore, introducing additional genetically unrelated adults into a family would likely increase the risk of child abuse.
The fallacy is to say that we can't have legalized polyamory because it's negative for the children, while we allow sistemic issues to have a much greater negative effect on said children.
> and nobody is abolishing your civil rights
Hello Texas? What are we even talking about?
> Civil rights don't mean you can do whatever you want.
I never said this, but if you needed to remind yourself of it go ahead.
While I don't necessarily agree with your stance about systemic issues, I would like to point out that solving them would take a lot more work than simply not legalising polygamy, and I don't see why we should neglect taking measures we are actually capable of implementing in favour of a pipe dream that might never be implemented.
I agree. You do both. If revolution is not immediately possibile, you fight for reform instead, hoping that it will sow the seeds of the revolution in those who fought with you. Any small victory for social movements generates a strong taste for solidarity and the expectation that the victory can be repeated.
Therefore, introducing additional genetically unrelated adults into a family would likely increase the risk of child abuse.