The end of the world as we know it?

"OK, so some people are going to say, 'Black holes? Those big things eating up stars?' No. These are microscopic, tiny little black holes. And they’re extremely unstable. They would disappear almost as soon as they were produced."

How do they know how about the stability of a tiny black hole? Not that I'm worried about them devouring the Earth, but still this all has to be conjecture.