Because almost half those gun owners are likely solid Democrats, and go around saying how they're "not a one-issue voter," or they "vote their paycheck," or some other thinly-veiled affirmation of support for the government taking control over one or several aspects of people's lives. (When they're not posing as Libertarians on gun forums, so they can attack Republicans from a position of disguise...or just threatening to stay home on election day altogether).
FIFY.
I'll give Trump one thing: he certainly does seem to be inside peoples' heads. I cannot remember the last time I've seen so much public hand-wringing and urinating and moaning about one primary candidate, out of a field of 15, and especially coming from so many people who wouldn't vote for any Republican anyway. If you're not a Republican, take two pills and give it a rest, people. "Your" primary ballot is located right next to the one with that big, bad, poopy-fascist rich man's name on it who chaps your azzes so bad. Grab the "other" piece of paper, put that little sticker on your shirt, and move TF on already. That evil little man will go back to his telly show, and you'll get 8 more years of the tried and true. I promise...
Obviously you weren't voting when Wallace was running.