The natives lost something, to be sure, but I'm not sure it was property. Property is created when you kick everyone else out. I assume that's the rationale behind "property is theft," it used to be everybody's and now it's yours.
You're correct. They didn't lose property as they had no legal concept of ownership. Instead they lost their homes, their culture, and their lives. How lucky for them!
The level of respect is per treaty, a blanket statement cant be corroborated as many are not respected or dont have consensus amongst the affected people of being respected