The books condemn bullies, falsity, rudeness, greed and Nazi-like tendencies to denigrate and hurt those who aren't like us. Rowling doesn't sugarcoat. Her characters can die or fall by the wayside. They struggle within themselves. But no worthwhile book, the Bible included, has only plastic people.
Life is played for keeps.
Good books reflect that. The Potter books measure up to William Faulkner's standard. Some claim the Potter books lure children into witchcraft. The Wind teaches young readers to be slave owners, or Treasure Island entices children to be pirates, or Peter Pan urges children to run away from home. If we started to ban books dealing with the supernatural, we'd be tossing out some pretty good stuff.