Could be both.

NEITHER..HE JUST TWISTED THE VEIN IN HIS BALLS.

I always thought it was both - Tre cried because of his victimization at that moment, as well as for this man who expressed such self-hatred before him... who had said something nice to Tre back when he was a child.

BTW, this film just had its 30th anniversary. I feel like applauding the acting in it. Someone I know had criticized one of the hood chicks from the backyard party who had her mouth open during most of the scene. I felt the actress was being naturalistic with her acting....