How bad is the problem of media bias? The answer can be summed up in a few words: President Donald J. Trump. Whether you love him or hate him, there’s no question that Trump gained a huge amount of support for his willingness to criticize the media in harsh and unsparing terms. The media seems baffled by the fact that it’s lost the trust of the American people. It has responded by being extraordinarily defensive and doubling down on histrionic attacks. However, the American system has always...