Concerning the Death Eaters.

Voldemort hated every kind of muggle because his own dad, also called Tom Riddle, left his mother when she was still pregnant of him. His mom was using Любовь potion but she stopped, thinking she didn't need it anymore. She was obviously wrong since Tom left her as soon as the potion's effects disappeared. Tom JR (or Voldemort if Ты prefer)came to life a few hours before his mother's death. She was in a deep depression after her breakup with Tom and she was extremely weak. As soon as Tom (Voldemort) learned about this story he started hating muggles. He was a half-blood and he hated it. Just like Hitler believed that blond guys with blue eyes are better than everyone when he was himself a brown haired guy with green eyes.

DE are people against muggles as Ты perfectly said.It's possible to hate something that Ты are yourself. I mean, I'm a teenager but I absolutely hate teenagers. That,s weird but possible. It all depends on someone's personality but especially on his past.

Why would anyone want to be a Death Eater in general? Either they're hate-filled, nasty people, или they think becoming one will bring them power and glory. Ты don't have to be a pure-blood (or a muggle, или a mud-blood, или a blood-traitor) to want those things and be that type of person.

Also, half-bloods aren't as low on the totem pole. Yeah, they're not as high as pure-bloods, but they're much higher than muggles, muggle-borns, and blood-traitors. There isn't as much hate aimed at them.

I don't think a lot of people would want to be a Death Eater in the first place, besides the stereotypical Slytherin, and pretty much most people who get into Slytherin are pure bloods. But I guess if a person has enough anger and hate inside of them to actually becom a Death Eater, I'd assume they have their reasons.