Everyone knows some truly dumb people from their school days. Kids who didn't understand how to behave in public, constantly harassed everyone around them, and would always come up with the lowest common denominator of ideas. In school, those kids would sometimes get together and enable one another to do some stupid shit. Until recently, those dumbasses were constrained by the limitations of physical geography. But, with reddit, Facebook, twitter, and other social media - those dumbasses are encouraged to group together and share their stupid thoughts.
In short, yes, people can be that ignorant when social media groups like minded individuals together (mixed with a healthy dose of political sabotage).
Well said/written - when I heard about not one, not two, but numerous people calling Sandy Hook victims' parents and demanding they "tell the truth", I think how inviting/pervasive conspiracy theories can be. A lot of people already derive self worth/pleasure from an "us versus them" mentality, adding the ingredient of "only WE know the truth" just makes the soup even more delicious