As I understand it now, a major reason, if not THE main reason, for Juan Williams being fired by NPR was that his contract specified that he was not to identify himself or be identified in his capacity as a Fox News commentator as "NPR news analyst" or the like, but Bill O'Reilly specifically referred to him as such during one of his shows.   The Bill O'Reilly show is taped and edited before airing, so Williams could have insisted that that comment by O'Reilly be deleted, but that did not happen.

I think NPR did not want Fox News channel or Bill O'Reilly's show, in particular, to seem to be legitimized in their "fair and balanced" claim by holding the inclusion of "an NPR news analyst" up as evidence thereof.   And that makes sense to me, in that Fox does not allow their token "liberals" free rein in asking probing questions or expressing ideas that challenge the Fox perspective.   In any event, if the contract prohibited Williams' being thus identified on Fox, that part of the contract was violated.