doctor who owns a nice house 2 cars and maybe a rental property has more interests in common with an oil baron

Yes he does and what’s more, he knows it! He’s not loyal to the baron because he’s an idiot. He’s doing so because he knows how his bread is buttered.

Yelling at him that he has “nothing to lose but his chains” won’t work because he has a lot to lose besides his chains. In fact he probably suspects (rightly) that his rental property, his medical practice and his fancy car will all be torched in the revolution long before anything happens to the baron.