I don't think the media on the left care about credibility anymore. They will publish lies, and then pretend there isn't video proving they're lying. For instance, The Daily Beast have reported that Ted Cruz is defending the Nazi salute, the video shows him saying that the parents did the Nazi salute because they were suggesting the school board are Nazis. Followers of this kind of media also don't care that it's a lie. This whole atmosphere of distrust only creates more conspiracy feelings.
It was probably better (for our mental health, and belief in institutions) before everyone carried a camera, and before everyone could publish on the internet. The media has been slow to adjust to the new normal.