Was Nazi Germany a police state to its self declared "true" citizens, i.e. ethnically pure Germans?

anyone who didn't share the nazi ideology ran the risk of being persecuted. even if they were "pure germans". this included socialists, communist, disabled people, lgtbq people, religious minorities for example the jehovah's witnesses, student groups and so on. so yes, like every fascist regime in history, nazi germany was also an extreme police state.

A large part of the people who were murdered by the nazis were ethnic German dissidents, LGBT people and disabled people.

That's who they started with. An important truth somewhat overlooked in mass media about them.

Yep. Even Rommel was murdered (forced suicide).

Imagine getting the benefit of his post war commentary. It would have been so enlightening. From what I understand, he was like Doenitz, a dedicasted military veteran from WWI grandfathered into the Nazi military, not a genocidal Nazi Party idealist. He would not have been hanged.
- He still idolised hitler for much of his career, was extremely racist and antisemetic, and contributed wholeheartedly to the german war effort. Although you are right, he wasn’t genocidal, and late in the war he became disenchanted with Hitler. He was one of the better Nazis, and wouldn’t have been hanged, but he was still awful. I’m very uncomfortable with the fact many schools and streets are named after him in germany, and that he has a couple monuments.

To "pure" citizens? No. They weren't a threat.

But they also decided who the pure citizens were.

Cross a line, annoy the wrong person, take the wrong photo at the wrong time, and very quickly, you could be found to be not so pure.

Then you were in trouble.

Dumb question but growing up I always heard Hitler wanted blonde hair and blue eyes even when he had neither. How was it they decide who was pure or unpure ?
- It's a simple question, but with a complex answer that I'm not sure I have the tools and knowledge to answer.
  
  But I'll try.
  
  The answer has multiple layers, on the surface, yes, the "Aryan ideal" was what they strove for, and the picture they put forward was blonde hair and blue eyes. On the surface, it was purely cosmetic, you had those features you were probably the Aryan ideal.
  
  But that wouldn't mean they would take an American prisoner who met those ideals and ship him off to the breeding center to help pump out perfect babies. Because they were inpure.
  
  In another layer, in reality even, the "Aryan ideal" was used like a tool. You were pure if you stayed in line and supported the cause, and the threat of being found not pure was used to keep people in line. The threat of the secret police, was the threat of them turning up to whisk you, or your loved ones, away, at even the merest hint of dissidence.
  
  By the end of the war, everyone knew someone who knew someone who had at least been questioned, if not disapeared.

Yes, extremist governments are unpredictable and you never know when Sauron's eye will turn toward you.