I think that in general Keith Ellison has been doing a great job of articulating what is wrong with the King hearings (although I can't tell if he has been effective in terms of changing minds).
What I would say is that the way you frame a question will determine the kinds of answers you tend to get. So when Rep. King chose to frame a set of hearings around the radicalization of American Muslims he basically chose to get answers which reinforce negative portrayals of Muslims. On the other hand, if you look more broadly at domestic violence and terrorism (George Stack flying a plane into an IRS building, Jared Lee Loughner's shooting rampage in Arizona, Scott Roeder's murder of George Tiller, George Jakubec's Esdondido house full of explosives, Roger Stockham's attempted bombing of a Dearborn mosque, the foiled Hutaree militia plot, and so on) other factors start to enter the conversation (how we diagnosis and treat mental health, the heated political discourse, gun-control, anti-government sentiment and much more). So by all means, let's look at the causes of violent extremism but let's not just look at a small slice.