As a martial artist, I find that when I fight someone, they potentially have more to learn from it than I do (if they are willing). I am not surprised that beating someone is referred to as “teaching them a lesson”. This is true of debate. I may strengthen my conviction and skills by having to present and convince, but the real reward is when others force me to change or reevaluate my position based on heretofore unknown facts and considerations.
The following TED Talk discusses this. Enjoy.