Have you seen any of these people on mainstream fora? The reason these people seem so common is that you're per-filtering your internet browsing to sites that strongly value truth.
I see these people in my everyday life all the time. I think that the edge internet contrarians don't realize their views are held as common sense by fairly large sections of the population.
I suspect there are many fewer such people in places where said edge internet contrarians live (e.g. New England or the Bay Area) than elsewhere.
(I've never been to New England nor to the Bay Area, so take this with a huge grain of salt.)
Suppose I told you that I knew for a fact that the following statements were true:
You’d think I was crazy, right?
Now suppose it were the year 1901, and you had to choose between believing those statements I have just offered, and believing statements like the following:
Based on a comment of Robin Hanson’s: “I wonder if one could describe in enough detail a fictional story of an alternative reality, a reality that our ancestors could not distinguish from the truth, in order to make it very clear how surprising the truth turned out to be.”1
1Source: http://lesswrong.com/lw/j0/making_history_available/ewg.