Fred, I think the experience with your neighbor is an absolutely PERFECT example of real, live PC. Often we tend to confuse such with simple misinformation or lack of experience coupled with a deceptive media. But those can be addressed by simple, calm discussion, friendly explanations, and/or (my favorite) an invitation to come along next time you go to the range.
But what I consider REAL PC is as you describe, totally incapable of even understanding a word you say, any small sign that you're not going to immediately agree with the currently PC point of view and they begin to lash out, calling you names, tossing around meaningless one-liners ("You don't need an AK-47 to hunt DEER!") and totally refusing to discuss the matter further.
Where do they get that way? Excellent question, my own supposition is essentially brainwashing at an early age, by parents or schools, churches, etc. When you have not yet gained the power of reason, like the 4-6 year old area, susceptability to brainwashing is awful high. And I personally reject the concept that all these folks are actually mental midgets, having known some who could hold their own with anyone as far as intelligence went, but trespass into certain subjects like firearms, race relations, smoking, homosexuality, etc, and you can almost SEE their minds shut down.
I had two brothers who were both very, very, VERY anti-gun, one from each of the camps I describe. Both spent great deals of time explaining to me all about why all guns should be outlawed, etc. I submitted reasoned responses to both, often at the same time, but only one ever heard me, the other visibly shut down, called me names, tossed one-liners like how I was gonna feel different when my kids killed themselves, etc.
Upshot is I now take guns along whenever I visit the one, and although he doesn't much enjoy shooting it doesn't bother him at all to wander out in the front yard and blast away with my AR or a hi-cap pistol or two, he occasionally joins in with his own (!) shotgun (He has 70 acres of woods). He is also a very staunch defender of 2nd Amendment rights, possibly due to the fact that in the process of changing his mind about guns I also (very early on) pointed out that once he had listened to both sides of the story it would become painfully obvious that SOMEONE was flat-out lying to him, deliberately, knowingly lying. And that when he got to that point he would have to do his own further research before he could figure out whether it was me or his other (overwhelmingly anti-gun) sources. I've used that tactic before with people capable of listening at all, and it invariably works, as it did this time. When honest people discover they've been lied to repeatedly, about guns or any of several other subjects, their views tend to flip-flop VERY quickly.
The other brother now considers us BOTH looney, will absolutely not even listen to a thing on the subject or several others on which he is similarly dug in. An idiot? Stupid? Sorry, he's an M.D. He is carrying some kind of baggage picked up in his childhood which he is incapable of putting down, and on those entrenched subjects he has not changed since he was in junior high!
You can mention that no one should be judged by his skin color, religion, etc. and he is right there with you, yes, yes, absolutely. State that discrimination in all forms should be stamped out and oh! he gets all excited. Suggest that we should start in that direction by abolishing Affirmative Action SNAP!! You can literally watch his eyes glaze over and the steel trap mind which is so wonderfully trained and educated snap shut in a split-second, and you'll never even get to finish the sentence before he's calling you a racist and a bigot and on and on.
What would be nice would be to figure exactly where and how that happens. People (some of them) end up with what I'd best describe as a conditioned response to certain words or subjects, and ever after cannot get past that conditioned response. And while not one of the "black helicopter" bent, I'd also like to know whether that conditioning is accidental.
At any rate, that is what *I* consider real PC as opposed to simple cowardice (won't go against the crowd) or lack of information.