Juan Williams wasn't let go because he's conservative; it's because he's a bigot (unless you think being a bigot is a conservative qualification):

"Look, Bill [O'Reilly], 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."

https://www.npr.org/2010/10/21/130712737/npr-ends-williams-c...

"NPR, like any mainstream news outlet, expects its journalists to be thoughtful and measured in everything they say. What Williams said was deeply offensive to Muslims and inflamed, rather than contributing positively, to an important debate about the role of Muslims in America."

https://www.npr.org/sections/publiceditor/2010/10/21/1307132...