I think we can agree that the Dursleys are one of the most loathed fictional families of all time, mostly because they were so vile to the Boy Who Lived. But why exactly did the Dursleys hate Harry Potter so much? I mean, they made a scrawny young boy sleep in a cupboard under the stairs... That kind of hatred stems from something more complicated than just a fear of magic.
Fortunately, J.K. Rowling has finally explained the root of the Dursley's hatred of Harry. They hated Harry not because he was an orphan, or even because he was a wizard, but because of his father, James Potter.
The ever-giving Rowling recounted the first interaction between the Dursleys and the Potters in a Pottermore post. Apparently, Petunia invited Lily and her then-boyfriend James over one day to meet her fiancé, Vernon Dursley.
Mischievous James Potter and blustery Vernon Dursley in the same room... What could go wrong?
The encounter between James and Vernon went south right away. Rowling writes, "James was amused by Vernon and made the mistake of showing it." In all fairness to James, Vernon's ability to turn beet-red in a millisecond is quite amusing.
After Petunia and Vernon fled the restaurant, "Lily burst into tears and James (a little ashamed of himself) promised to make things up with Vernon at the earliest opportunity." This never happened, though, and thus Vernon's hatred of James was left to marinate.
This blow up caused the rift between Lily and Petunia to widen. Petunia didn't even ask Lily to be her bridesmaid at her wedding! Lily and James attended the wedding, though, where James overheard Vernon describing him as "some kind of amateur magician." Sure, an amateur magician who could conjure a kickass Patronus.
Following Harry's birth, Lily wrote Petunia a letter informing her of the good news. Petunia threw the letter in the trash. This was the last correspondence between the sisters. Imagine Petunia's surprise when her infant nephew appeared on her doorstep a little over a year later.
Petunia took Harry in, though, when she heard about the horrible way that Lily was murdered. "She did it grudgingly," Rowling wrote, "and spent the rest of Harry's childhood punishing him for her own choice."
Snape, however, didn't let his dislike of James Potter get in the way of protecting Harry, even though at times it seemed like nobody hated Harry more than Snape. This was Rowling's way of showing that love can overpower hate, something the Dursleys were never able to understand.
In case you were wondering exactly what Rowling's thoughts on the Dursleys are, here is an excerpt from one of her Pottermore posts: "The Dursleys are reactionary, prejudiced, narrow-minded, ignorant and bigoted; most of my least favourite things."