The RINO pathology
Your first three paragraphs seem reasonable and straightforward. It's the fourth paragraph that I think gets to the root of the attitude that produces the "RINO" pathology:
The Democratic definition of a "reasonable" Republican is one who adopts Democratic positions and policies. See also: Arnold.
I've said many times that living in a democracy obligates an American to work with, and not against, fellow Americans; and to find common ground through compromise, for the good of the country as a whole. Yet, as often as I've said that, you've responded with a thunderous denunciation of compromise as a betrayal of principle. That right there is the problem: You and too many Republicans elevate ideology above citizenship and civic duty.
Of course an extremist would call Schwarzenegger a RINO. Arnold's done fairly well finding common ground and getting people to work for the common good. He's not universally popular, but he's not polarizing either. The fact that that makes him a pariah says more about how dangerously deranged Republicans have become than it says about Schwarzenegger.
America needs RINOs now more than ever.