What are the dangers of Donald Trump branding news items as "fake news"

A vital part of an democracy is its 'fourth estate' - the free press. Without a media that is free to report on the activities (and possible wrongdoings) of the government, citizens are in no position to make informed decisions about who they are voting for, since they are in the dark about what their potential leaders are actually up to. So without a free press governments can get away with shaping the nature of debate and close down other ways of looking at things. However, the downside of a truly free press is that they are at liberty to say anything they like, whether it is accurate or not.

In the US there has been a proliferation of news and opinion channels over the last thirty years, particularly marked by the rise of often right wing talk radio and, of course, Fox News. These media sources have been joined by internet based commentators and news sites. The nature of internet news, and how it is shared on social media, is that it becomes increasingly difficut to know what is or isn't a trusted source, when news and opinion sites big and small, trustworthy and untrustworthy, can have similar branding and both look equally bona fide. This is what led to the 'fake news' controversies of the 2016 election, where entirely invented stories attributed to sites that looked like they might be genuine news sites, were shared on social media by people that wanted to believe they were true.

Many of Trump's supporters are consumers of more opinion than fact based channels, such as Fox News or Bretbart. The consistency of opinions that come out of such sources can often be so at odds with the more mainstream media that it leads to the feeling, from trump supporters, that there must be some sort of liberal media conspiracy against what they see as the truth.

When Donald trump casually brands critics, or even dispassionate observers, including CNN and even the UK's highly regulated state broadcaster, the BBC as purveying 'fake news' he is helping to create an environment where the only truth is what news consumers choose to believe, and thus where voters are increasingly unable to make informed choices about who they vote into government.