Friends are tough, huh? They can be good influences (like Rufus) or bad influences (like Buphead), but either way, who we choose as friends and how we treat them has a lot to do with the kind of people we become. In The Watsons Go to Birmingham—1963, Kenny has a bad friend experience with LJ the Dinosaur Thief, but this helps him to appreciate just how good of a friend Rufus is. But Kenny and Rufus don't have a completely smooth ride either, and Kenny almost loses his friend when he joins the crowd in teasing Rufus about being poor. Kenny realizes that if he wants to keep his friends, he's got to be willing to stand by them—even if it means getting picked on himself.
Kenny is wrong in the beginning to put his own self-interest ahead of befriending Rufus.
Kenny knows that if he and Rufus become friends, the bullies will pick on both of them twice as much, so it's okay that he avoids Rufus in the beginning. He's just trying to protect them both.