For the most part, though, I think being overly generous leads to bad habits. You get better as a player when you suffer the consequences of those mistakes.

It's pretty remarkable how often this is cited as reasoning, when pretty much all behavioral and educational research demonstrates that negative reinforcement is actually the worst way to learn something.

If your goal is actually to help your opponent learn, you might want to change how you do it. (If that's not actually the goal, that's perfectly fine -- it's not your job -- but you might want to come up with a different, accurate, rationale for how you handle his newbie mistakes.)