What is David Concerned will happen if his grandfather finds out about his uncle? what prior events support this concern?

Grandpa Hayden is described as being extremely racist, not considering Frank’s actions as being something worth punishing because he only molested Indian women, a race not considered worthy of being treated in a just way by Grandpa Hayden. When Wesley decides to hold Frank in his basement and then take him to the city jail, Grandpa Hayden comes to him, demanding to release Frank. When Wesley refuses to do so, Grandpa Hayden stops talking with Wesley and with his family, severing all the ties he had with them.