1. Encounter said bullies or kool kids
2. Wait for your friend to take their side
3. Falcon Punch
4. ???
5. Profit
There is simply no other way around it. If you can't talk any loyalty or reason into that "friend" of yours, ignore him in the future. So you aren't good at the social standings, but so what? Does that make you deserving of a backstabber who enjoys hurting the vulnerable?
If he dosen't say anything along the lines of "O, I've never realized how terrible I've been" after you explain to him what you've always thought, then its a good time to forget about him and move on.
Sounds to me you've always been conservative and mostly a target in school. Get some balls and start changing your life.