shibumiseeker
Grandmaster
I haven't looked at the critique yet, but the selection bias is using those who have been shot as your treatment group is profound.
Yet since most people don't have any clue as to how proper sampling or research is conducted, the "study" serves its purpose: to give justification. Since most people who fear guns can't point to any rational reason for their biases, this gives them something that can strengthen their resolve and immunize them against seeing other possibilities. To that end, it works very well. As a political tool it's tried and true and time-tested, playing on fear and ignorance.