My ex-wife was that way. She would almost ALWAYS send something back, complain about this or that, and then bitch at me for leaving a big tip. One of the biggest fights we ever had was when I told her once, they deserve every penny of it for putting up with you! lol
I worked in a restaurant when I was in college, and I don't know that liberals or conservatives matter with tips, but I can tell you this, wealthy women are usually the worst of the worst. My best tips usually came from those you'd least expect.
I think people who have worked in the business are more generous.