People generally don't understand astrophysics. High school science classes generally concentrate on biology (baby pigs are cheap) and chemistry (most of the students probably understand how to make meth better than the teacher). Usually one or two experiments in physics, generally dropping things.
Secondly, people just understand that black holes are Bad Things, the "most destructive force in the universe" (thank you Disney) and that the universe will end with a Real Big One, because that's what they saw on the History Channel. I won't fault people too harshly for this, but it doesn't take a Einstein or Hawking to figure at least the basics out. I'm somewhat shocked that learned people are perpetuating this ballyhoo about black holes at the LHC.
People have a hard time with very small and very large things, so I usually put things in terms of the Sun. Yes, I know this is a very large thing, but they can at least see the sun and have an idea of its size. Should the Sun suddenly become a black hole, we won't get sucked in as most lay people think. A black hole with the mass of the Sun is still an object with the mass of the Sun and all the properties that go with it, such as gravitational pull. The earth will continue to orbit just as before, but it will become cold and dark. That's it. A black hole created at LHC from two particles will have the mass of those two particles.
And if I'm wrong, well we'll likely die so quickly that it wouldn't matter anyway.