Why did Papa go after Charlie Simms?

Papa did not go after Charlie Simms. Uncle Hammer went after him because he found out that Simms knocked Cassie off the sidewalk, but Mr. Morrison stopped him. In Chapter Eight, Papa gives Cassie his reason for "not" going after Charlie Simms.

Now I don’t like the idea of what Charlie Simms did to you no more than your Uncle Hammer, but I had to weigh the hurt of what happened to you to what could’ve happened if I went after him. If I’d’ve gone after Charlie Simms and given him a good thrashing like I felt like doing, the hurt to all of us would’ve been a whole lot more than the hurt you received, so I let it be. I don’t like letting it be, but I can live with that decision.