I'm going to offer a different perspective here. Like you, I'm from a rural area that doesn't have money. I went to a title 1 public school. Like you, it's clear that my graduate program is full of people who come from educated and wealthy backgrounds. And yes, like you I sometimes notice a condescending attitude toward those who don't come places of equivalent status or privilege.

But really - who cares? I accept that these people have lived in a very particular environment their entire lives, and they can have hilarious interpretations of what the world is like outside of that environment. This is acceptable and completely expected. You should try approaching your differences more diplomatically, or perhaps ignoring them altogether. I can't imagine they get the chance to make these comments very often. I think you'll find these people are not as different as you think, and approaching them with more understanding would help you get along with them.