I think this thread was a great idea. I know that I need it, because I don't get a lot of opportunity to go practice like I would like to do.
You make a good point about ego, and you're correct in saying that people (such as certain LEOs, for instance) can use their ego as a shield because they're afraid of criticism. Instead of just laughing it off and moving on to someone more receptive, I challenge anyone who serves as an instructor to accept getting that person to let down their guard, put aside their ego and trust you with their emotional vulnerability, so that you can truly help them prepare. Plenty of egotistical, hard-headed guys in the military who probably wouldn't be alive if some NCO hadn't cared enough to punch through that outer wall and used that opportunity to teach them life-saving lessons.
Some people are hopeless - they just won't let that ego fall away in order to learn. However, there are those who just need a teacher to make that little extra effort to get inside their mental and emotional wall, make that connection between teacher and pupil, and use that connection to, in this case, hopefully save a life down the road. Teachers cannot always tell which is which, and it's your call whether to make that extra effort, but I ask you not to dismiss someone just because they're a little more hard-headed. They might just need you to peek under that outer shell. That egotistical asshat at the range might just be the most trustworthy friend you could ever meet, if you can get under his defenses and give him a chance.