I am incredibly liberal and I used to love Michael Moore's documentaries until I saw that in fact he does lie in them. I am not just talking about little white lies either. I learned all this from the documentary "manufacturing dissent". I would highly recommend it if you want to understand why you cannot trust a word Michael Moore says.
His whole movie Roger and Me focused on how Roger Smith, the CEO of GM, wouldn't meet with him no matter how hard he tried. That is the focus of the documentary, but the reality is that he did meet with Roger, but cut it from the film. His documentary about capitalism is all about how greedy the wealthy people are and how they will never let "us" become wealthy. Michael Moore has made 120 million dollars from his documentarys and he lives in the lap of luxury.
After watching that documentary, I'm convinced that his game plan is to make money by making propaganda style documentarys about whatever the most popular issue is of the day.