"out after saying Jews are not oppressed minority" or maybe, if you actually listen to the interview, because of accusing Stewart of being a bigot and basically pulling the "Elders of Zion"/(or a "Mel Gibson" if it sounds more familiar to you) shtick? I think it used to be called anti semitism.
Your headline suggests causation. Sanchez has had bad ratings and been infamous for gaffes for some time. This incident could have played differently were he a hit. (CNN is where Lou Dobbs perfected his anti-Mexican shtick.)