I would like to present a slightly different point of view. Respect needs to be maintained. To my mind, saying respect must be earned, means that no one is worthy of respect until certain criteria are met. Again, not trying to be antagonistic, this is JMHO.
I prefer to treat everyone with respect until they act in a manner that makes them unworthy of that respect. When my time on this Earth is done, I shall be judged by what I have done, and not by others reactions to what I have done.
That I was kind, helpful, or courteous, that is on me. That someone called me a pig for doing this, that is on her.
But then...when something is maintained, it is a continual earning of that respect...same thing.
Bingo!