The ?????? I think comes from the relationship itself, irrespective of the mitzvah.
I agree that it is bad middos to feel insulted, but at the same time, it I think it is also their right. But that is their problem. My problem is to make sure that they don’t get put to that test to begin with.
Again, I’m separating the mitzvah from the relationship.
Dama ben Nesinah didn’t have a mitzvah of kibud av, yet he was still rewarded. I think this is because regardless of the mitzvah there is still this inalienable relationship that exists and he exemplified it.