It's worth remembering, too, that there were scientists, reputable ones, who were afraid that setting off the first atomic bomb could destroy the atmosphere. The science said it was extremely unlikely but, as noted earlier, scientists rarely can say something is impossible. There were also fears about that big collider in Switzerland. But it's already been run and, lo and behold, no black holes eating up the Earth!
The point is, there will always be those on the margins who will play up the extreme possibilities, whether through honest concern or simply to get their faces on the news. Just remember: while a 99.999% probability may not be the same as absolutely true, it's a hell of a lot more likely than driving home from work without having an accident. Worrying about the .001% will keep you huddled in your home, afraid to open your eyes.