It sucks that your friends think poly is wrong and don't get it. Not uncommon though. I would suggest getting out to poly events and getting to know poly people so that you have a sense of belonging and get support from friends that understand.
My friends had all never heard of polyamory and I dont blame them, neither had I. There is difficulty in trying to convey what it is as I'm sure you all know. No matter what I say about trust or honesty or free love, the second I tell them he has another gf they tell me I deserve better. So it was really hard for me because I didn't know who to listen to. I choose not to tell most people and some of my friends just want me to be happy, but they still feel sorry for me. I just wish they could see what an amazing guy he is.