Not many reporters get fired at CNN  They canned  Donna Brazille for handing Hiliary the debate questions before the debate. But many other stories were repeated, without evidence, and no one lost their job. 
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Media bias is never going to go away, but we should expect to hear the truth from those with the biggest platforms to propagate from. 
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Some of them get fired and re-appear at another news outlet, like Rachael Maddow who was fired after lying about Rush Limbaugh back in 2011.  But many do not get fired when  the story just can't be verified one way or the other and the 'sources' are invisible. They may not even exist, we'd never know.
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As far as Trump being a 'proven' compulsive liar, I'd have to say, no more so than the left wing media. I think if Trump lies at all, he is lying to the liars in the media and Hollywood and they really do have it coming. They've been covering for their liberal friends long enough. Time is up.