No need to let such a slug ruin it for you.
How long has this guy been on? If its more than a year or two, he's no rookie, knows better, and is just being a PITA because he WANTS to. I had some of these over the years. The best way I found to handle them (assuming they didn't do anything I could boot them off the range for, such as disrupting the class, safety violations, etc.) was to ignore them.
This kind of guy is simply not worth your time and the heartburn needed to deal with him. He relieved you of any obligation to help him by deliberately ignoring the assistance/training you offered and by going out of his way to complain, etc.
The only individual more annoying than one of these clowns is the "gun guy" who thinks he knows more about the game than you do. These require a bit of care, but you can shut him down right quick if you play it right.
You might be interested to know that the average LE firearms instructor lasts five years before he burns out. Some sooner, some later.
Welcome to the game. I played it for a bit over 20 years.
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