Character Analysis
Guilt by Association
Some people, like Erma, are terrible people because they do terrible things. Mom even makes a Hitler reference with Erma. When she tells Jeannette that everyone has good qualities, she says, "Hitler liked dogs" (3.4.36). Okay, Mom.
If Erma is Hitler, then Grandpa and Uncle Stanley are the people who blindly follow Hitler and become Nazis. They do nothing to stop her behavior. Uncle Stanley himself inappropriately touches Jeannette. Considering the fact that Erma likely touched him in a similar fashion, it's sort of understandable, but it's certainly not excusable.
Abusive behavior usually begets more abusive behavior. It takes people like Jeannette and her siblings to break the cycle.