Fake news is a problem because it is crafted to deceive, and it isn't all fake. It takes a moments lapse in judgement to begin believing that the world is flat or hollow or all the world's leaders are lizard aliens. But there are believers. When fictitious truths are presented and repeatedly enforced, with slight variations (as tends to happen with truth) the challenge grows.
There are very few of us who have not passed along or posted something which turned out to be false, despite assurances to the contrary from our friends, neighbors or brothers-in-law. We have all certainly received fake news from friends, relatives and strangers, both innocently and maliciously.
There is no excuse for ignorance. It may be unfortunate and inconvenient to view everything as possibly false, but it is outright dangerous to accept everything you are told as true.
But it all gets terribly tricky doesn't it. There is a major difference between a story or article having a grain of truth and being true. A coincidence does not make a conspiracy. If it did conspiracies would be a daily event. I doubt that very much. Anyone who tells you what to believe is trying manipulate you. The same for anyone not willing to hear what you have to say about what you believe.
Taking a few minutes to do a little research on news stories and ideas can benefit everyone. Informed opinions and ideas have long been the foundation of a stable society.