What a terribly sad story but I agree fully with your A/N.
It's one reason why I like some HP stories where Harry goes dark or just outright refuses to save the world. It was very clear in canon that Dumbledore FULLY INTENDED for Harry to suffer the Dursley's abuse and there is NO doubt it was both physical and mental by the quotes from the books.
I feel that there HAS to be consequences for the world if they stand by and allow such cruelties to be inflicted upon a hero. If that is how little they truly care for those they hold in highest esteem, then perhaps they deserve to die.