I don't have disrespectful friends, I know disrespectful people.

Also just because someone is from a certain doesn't automatically make them understanding.

Most people just want others not to judge them while they are busy judging others.

Keep distance. Explore yourself.

I'm not sure your friends are the big problem. I looked up what polyamorous means and think for starters you are too young for "adult like" relationships and it's sad to see your age group asking about this and also saying you have more than one person you are intimate with.
It's not a good or healthy thing for anyone.
To your friends, it probably IS gross. If they are your age group, they probably lack in the thought of keeping their opinions to themselves.
People tend to be more understanding of their own ways, not others.
I hope, if this is a real thing... for your sake, that you maybe get some advise from adults you trust and I hope you have a change of mind and just be a teen for a while longer.