Everyone hates me and wants me to take sides?

help! my group of friends are gaining up on my one friend because they hate his guts for some reason and are terrorizing him by bullying him. He has messed up in the past and i understand that they would be a bit mad...but no one...I MEAN NO ONE deserves to be bullied and humiliated in front of everyone. (which is exactly what they are doing) anyways i supported him when he needed it and then they accused me of "taking sides" now everyone hates me and won't talk to me. i stood up for what i believed in and got hurt. i am soo upset right now. what do i do now?