Why are the dumbest people those who express their opinion the most?

So many people consider themselves smart but aren't. The more they talk about their theories themore dumb they are. Why is it that the dumbest people talk the most while moderate and measured people talk sparingly. Pretentous people, People who say that "there is one political system that will work for every scenario and I know what it is" or "Summer love is unethical (but me stealing a DVD from a dirt poor retailer in Nepal isn't)" or "Hitler was a hero and Churchill was evil, if he had left Hitler alone less people would have died. Evil pr*k". They talk all the time to reinforce their theories, and think that people don't understand them because they are too smart. They make smug comments and look down on people they see as inferior, when in fact, they are the ones who make no sense. Are these people deaf and blind. I'm a very opiniated person but I do like to think that I am measured and make sense. Some people make no sense, and they talk more than I do. Why goes through their minds? DO they just seek controversy? Are they egotists?