Harry Potter and the Weasley family

Exactly. And if you treat a child that poorly, you might as well turn him into a monster. Just look at Tom Riddle a k a Voldemort. He too grew up in a loveless environment (an orphanage), but he was a totally different person. His only dream was to be special and use his awesome powers to control other people... Harry on the other hand never believed that he was special, even after he found out about the prophecy. He never had any wish to be a celebrity and was mostly kind to other people. And he only became some wizard messiah because he simply had to. And as soon as Harry saw Tom's reaction to finding out that he was a wizard in the pensieve, he remarked upon how very different it was from his own reaction to the same thing at the same age. So I have to really cry bull**** on that letting a poor child be abused and neglected will automatically make him a better person.

I guess that the abused orphan is a staple in British literature (think of Jane Eyre and David Copperfield), and JKR wanted to follow that old tradition. But yes, you want to strangle Vernon and Marge.