Considering my feelings on the NRA, I can't say I care very much about him touting his propaganda at an NRA convention. I can't imagine that many people who go to such things are in the mood to have their eyes opened.
No more or less than the rest of the human race. A certain percentage, when they think they know the answers, think they already know all about it--why would they consider further when they know all about it?
Our job is to get over, through, and around those pre-conceived ideas and widen their perspective, and win, if not their warmhearted agreement, at least their willingness to respect OC.
I can offer a good example from myself. Once upon a time I considered conservatives and republicans to be the best philosophy going. My disagreement with Dems and libs approached hatred, and I thought the libertarians to be kooks.
Then one day a forum member here, Tomahawk, dropped a few lines and links here and there. I checked into libertarian philosophy and economics. Wow. I was almost offended by some of what I read. But, across time I shifted my views, persuaded by what I read and the analysis of members here. It wasn't easy to drop my pre-conceived ideas. But, I did. It just took some gentle persuasion and reading without browbeating or criticism of my existing views. Now, I'm pretty well aligned with all but the most hard-core ideas of the hardest-core libertarians.
It can be done.