I don't mean that humor can't be realistic, but that when someone says "that is inaccurate, and a bad representation of that lifestyle," the rejoinder is often, "well, it's funnier this way, so that's why they did it."
Roseanne was a reasonably accurate working-class-life show--but working-class families don't talk to each other like that, not and stay together, because what's funny in passing from a distance is a lot less funny when you're facing it every day.
From what I've seen of SPN, yeah, it's a lot less "working-class life" and much more "rugged survivors, defenders of good people, take on Teh Eebil Goosties". And of course, 'rugged survivors' are poorly-educated and have working-class backgrounds.