As bicker and many people have said, respect has to be the default or starting place. If not, one starts out without showing any respect and then when one realizes the person deserves it, it is too late. I've always hated that quote, or at least I've always felt it wasn't well thought out. It seems that is people followed that, they would end up not respecting many people. Furthermore, unless they learned to "fake respect," they would end up with many societal problems. Does it make sense to withhold respectful behavior until you think someone has "earned" your respect?
Also, for me, those who are soldiers, firefighters, police officers, nurses, teachers, etc. have already earned respect from me for earning a degree, passing difficult tests, choosing a career where hard work and helping others is placed over making easy money and by providing services from which I benefit.
If someone is not doing something well, there are ways of handling it without sounding arrogant, entitled, short-sighted and ignorant like saying "I pay your salary".