Looking back at my own similar situations from back in high school, three different possibilities can come from this:
1. You ignore it, take the harrassment, and the thought of this guy haunts you and pisses you off FOREVER.
2. You fight the guy, and lose. You're now even MORE pissed off and the feeling of defeat and loss of pride haunts you forever.
3. You fight him and win. You reign supreme and fuck his girlfriend.
phriend or foe...who'll ever know?