In That Was Then, This Is Now by S. E. Hinton, what stops the boys from beating up the black man?

In Chapter 1, M&M leaves the bowling alley and is confronted by Curly Shepard and two of his friends. Fortunately, Mark and Bryon leave the bowling alley to catch up with M&M and see Shepard cut M&M's medallion off of his neck then knee him in the face. Mark and Bryon attack Curly and his friends and save M&M from further abuse. After M&M's attackers run off, Mark looks at Bryon and says, "You still in the mood for a little action?" (Hinton 8). Bryon says he's up for it, and Mark signals towards a black man standing at the intersection waiting for the light to change. Mark says, "We could jump him." (Hinton 8). M&M then yells, "You make me sick!" and tells Bryon and Mark that he thinks their weird (Hinton 8). M&M says that Bryon and Mark just saved him from getting beaten up by people who thought he was different, and Bryon and Mark were going to beat up an innocent black man for the same reason. Bryon mentions that M&M looked real shook up, and M&M begins to cry before he takes off running. Instead of chasing M&M or beating up the black man, the boys pick up M&M's medallion and head towards Charlie's bar. M&M stopped Mark and Bryon from beating up the innocent black man by intervening and telling them that their actions were senseless.