Why is it some people trust corrupt politicians on the War, but not the leaders that are actually there?

Yes, I am talking about Petraeus. It seems that some people (i.e. people at Moveon.org) think of this man as a traitor for mearly giving his POV on the War in Iraq. I was just wondering, for the people that would rather trust people like Dennis Kucinich, who was talking about how the War was based on lies in Syria, the place that is giving terrorist a place to sleep, plus weapons and many other things, then the people who are actually there, and actually see what is going on.