I can't add anything to Carl Sagan, really. There is a saying about religion, that people who don't believe in it will believe all kinds of even dafter things, and the same is true of earthly knowledge.
People who don't trust the result of years of patient accumulation of data and the putting together of thousands of observations can latch on to the ravings of some fantasising fanatic. They don't have the knowledge or experience themselves to look at all that data and reach a conclusion, so they take as gospel the way that two completely unrelated things have been presented to them as affecting one another.
Add to that the way that every student exercise - carried out by someone who has had one year of learning the basics , and intended only to give them practice in doing all that data collection - can be triumphantly published online, picked up by a media reporter who knows absolutely zero about the subject but is hungry for copy, and treated as the latest expert research. A lot of the more outlandish "Scientists say that . . . " news items are of that type.
For some hilarious examples of false ,see www.fastcompany.com/3030529/hilarious-graphs-prove-that-correlation-isnt-causation though these were collected deliberately for a laugh - they weren't quoted as true.
