Muggle supremacy

"That's where you're going. A special school for freaks. You and that Snape boy… weirdos, that's what you two are. It's good you're being separated from normal people. It's for our safety."

- Petunia Dursley talking with Lily Evans about Lily and Snape

Muggle supremacy is an ideology regarding Muggles are superior beings while wizards and witches are some sort of unnormal or even retarted freaks.

The only known racists against wizards and witches in the novels are Vernon and Petunia Dursley, the stepparents of Harry Potter.

The Dursleys eventually led their son Dudley Dursley also into disgust of magic people, although Dudley's reluctance may primarily based on fear, not hate (for example, Dudley's first encounter with a wizard resulted in him getting a pig tail). While Vernon and Petunia often showed their strong hate toward the whole wizarding world, Dudley obviously do not hate all wizards, as he never insulted or bullyed someone just because that one had magical abilities.