It has been polemic for over half a century.
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“Journalists” have always leaned left but they were not quite as openly aggressive in promoting their favored candidates, condemning all things conservatives, and generally pushing a radical socialist agenda.
Its gotten noticeably worse in recent years. Its now in-your-face all the time.
Howard Zinn was a Commie indoctrinating students and teaching them the tricks of the game.
Other activist journalists came in as Communists. This was academia ensuring that they became Communists (if only to get ahead).