He doesn't want to admit to himself that he has wasted the best part of his life doing what was wrong and his fault.
Here is an analogy:
A guy learns a 'traditional martial art' (TMA) for 15 years. He learns pressure points, horse stances, kata (rehearsed forms), etc. Then he is he runs into a guy who has 4 years training in Brazilian Jiu Jitsu / Muay Thai. They do some friendly sparring, and the BJJ/MT guy easily taps the TMA guy out many times in a row.
This is very embarrassing for the TMA guy because he is supposed to be way more experienced. So instead of cutting his loses and admitting to himself that he has been training in an outdated system of combat he begins to make excuses. "I couldn't do my moves on you because they would permanently harm you", or "sure I tapped out when you had me in that choke hold.... but if I had reached back and placed my pinkie on this part of your temple....your spinal chord would severe on spot.... that is why I couldn't do my move"
When I hear TMA guys talking like this, it just means that they don't want to admit to themselves that they have committed so much time into training in something that is not as affective as modern training techniques.
Back to the 40-year-old-nice guy.....
He doesn't want to face the truth. It was his fault he acted like a supplicating nice guy. It was his fault that the way he was acting was turning girls off. It was his fault that (insert behavior here).
Now you show him a more efficient way and he gets defensive. He doesn't want to admit to himself that he has committed so much of his time in acting like a 'nice guy'. There is just too much truth here for him to handle, so he pretends that he would never had done this stuff and that it is just 'bull$hit' and that he wouldn't want to do it anyway.
