Regarding gun control specifically, these tactics do nothing to foster understanding between opponents, not to mention consensus of any kind. Still, to me, the more interesting and important issue is the nature of the debate itself. It may be understandable that people argue in nonsensical, counter-productive ways without realizing it, but it’s harder to understand, and to defend, when these things are at the forefront of the conversation. Limitations on cognitive ability or effort may provide part of the explanation, but not all of it. It is becoming increasingly clear that there is something other than pure reasoning going on: see, for example, Haidt's elephant and rider analogy, Kahneman's system 1 vs. system 2 thinking, Lakoff's metaphors and frameworks, or Kling's three axes model. I am nonetheless surprised to see the aggressive opposition to reason that I have encountered recently, and I wonder how typical it is.
Clearly we don't understand these psychological issues entirely, and if everyone could be aware of the things we do understand, we wouldn't have agreement on every issue that is currently contentious; but it would be clear where the disagreements really lie, and surely some areas of disagreement would be eliminated, if we were all on the same page about how the reasoning is actually happening. So should we strive toward greater enlightenment as a means of resolving (or reducing) conflict over public policy? I'm inclined to think that this is unrealistic. More likely we as a society will have to take these weirdnesses in mental processing as given and do the best we can in the face of them. For example, rules of evidence can be viewed as a means of managing jurors' potential irrationality, rather than trying to break through it (or pretend it isn't there). I have new respect for this approach. What to do in broader contexts, I have no idea. Yet.