I very much agree @creative_writer it baffles me how people can be so bigoted like... My guy, if it's not hurting you directly why get your knickers in a twist over it? When hating on anything takes sooo much energy? Bewildering.
Also don't know if you know this but within the polyamorous and ethical non-monogamy community, there's a general consensus that we practice polyamory NOT polygamy. There's more detailed info here, but basically polygamy has, as you say, a lot more of a cultural context, and often (but not always) involves coercion (e.g. an arranged marriage), hierarchy, and typically is centralised around one man with many wives. That's not to say it is overarchingly inherently wrong; as with anything if there is informed and enthusiastic consent, then go for it! But most polyamorous folks I know would be pretty miffed if they were called polygamous. Ach, semantics lol.
Sounds a little like a catch-22? Like... You won't know if someone is going to be safe for you unless you can open up and be yourself around them, but to be able to open up you need to feel safe first... am I onto something there?
What are some things you feel you have needed to hide? Or in other words, which aspects of yourself do you not feel safe to be open about? I know that's a big, potentially invasive question so please don't feel pressured to answer btw 💜