Have you ever been able to sense yourself NOT joining?  In this case, have you not joined out of fear or revulsion or anger?

What did you learn from that?  Why did you intend to join in the first place?

Peace is not a static goal anymore.  It is about joining whether you want to or not.  It is about bringing yourself to the fight with a plan for not fighting out of misunderstanding or hate, but just because you want a fight.  

How to stay in the fight without fighting, that is defending yourself but not being anger driven or fear driven, like my usual self.

The Buddhist answer would be to know yourself enough to give yourself the choice.