It's hard to say anything about this without actually seeing how you tank. That's the hard part about discussing tanking. Rotations and skill usage is just the very basics of tanking. Positioning, pacing, pulling method, marking, etc., all plays a part in how you ultimately present yourself as a tank.

One thing is certain, though. He's not being elitist, he's being a jerk. Elitist is giving you suggestions that you may think is impossible but which he can achieve himself; being a jerk is bashing you on your play without offering any constructive criticism.