Jon Stewart can be a very good interviewer when he knows his subject. His interview with Betsy McCaughey about the ACA always comes to mind. However, when he hasn't read up on a subject, misinformation can win the day. Social insurance is often one of such topics for misinformation.
I debunked some of the myths and lies on the show from interviews with Charles Krauthammer, Robert Reich, and Alan Simpson over at the Daily Kos. I'll just link to it to make life easier.