To have a moral compass is t have a basic set of rules that has basically been hammered into us since we were children. For example let’s say that robbery was happening every day and everyone was used to it, then you wouldn’t think that it was so bad and having no robberies would be a bit weird. Everyone has a different moral compass but everyone has the no killing no stealing stuff in their compass.
About the story the misfit is a murderer and robber who says that he has no moral compass. Without a moral compass the misfit only kills and steals because he feels like it and wants to.
Another person in the story is the grandmother whose moral compass is a bit old timely and she was a bit racist but she had the no murder and no stealing like everyone else. Unlike the grandmother the misfit is okay e\with everyone.
Morals are different for everyone but most people have the basic morals down which is why our world doesn’t normalize stealing and murder.