I pass a student of mine standing at a table with a petition.
"Hey Professor, would you like to sign an anti-fracking petition?"
"No, I don't really know anything about it."
"What do you mean?" He looked dumbfounded.
"Well, I would need to read up on it for a while before I signed any petition, either for or against it."
"Oh, I can tell you: it's bad!"
Given the amount of studying that my students do, I would be willing to bet that he knew no more about the subject than I know. But he made up for that with lots of extra certainty.