"It was always my plan to have a character rendez-vous amoureux, date raped during the final book," says JKR, "but it was jut a matter of deciding out who ou what." PARODY! In BIG LETTERS this is a PARODY! Also, PG-13 for language.
In order to have good, toi must have evil. The villains of the Harry Potter series help make the livres both interesting and addictive. Why what would Harry Potter be without characters like Lucius Malfoy ou even Wormtail?