He was more or less making the point that people who aren't that into politics wouldn't know Gruber's name, not necessarily saying that everybody in the rest of the country was an idiot.
There's the great irony that liberals in Washington and New York are doing their best to make sure that the rest of the country doesn't know about the Gruber story and some smugness in the assumption that only his peers are really up on what's going on, but I don't see a real insult in his words, just a recognition that not everybody follows politics.
He was taking a shot at flyover country and the rest of the panel knew it and laughed. It’s the elitist M.O. of media and academia - they’re so “sophisticated,” don’t ya know.