You people have no clue why he was hired, do you? He used to work for NPR.
"NPR terminated his contract on Wednesday, October 20, 2010, two days after he made remarks on The O'Reilly Factor.[11] He had commented, "Look, Bill, I'm not a bigot. You know the kind of books I've written about the civil rights movement in this country. But when I get on the plane, I got to tell you, if I see people who are in Muslim garb and I think, you know, they are identifying themselves first and foremost as Muslims, I get worried. I get nervous.""
He is a liberal from NPR, but he's human, too. Fox picked him up as a PR stunt because he got shit canned for hating sandniggers. It also helped to lend credence to "Fair and Balanced" slogan, having an opposing viewpoint in the studio.