I'm still guessing it wasn't about physical strength....but that aside...
The outcome very obviously bothers you.
You obviously don't think he let your son beat him.
You obviously think your son is stronger than him.
...if I let let a boy beat me, and the his mother jumped to the immediate conclusion that her son was stronger than me...and she didn't listen to hints that 'uh, are you crazy - I let him beat me' ...I'd also start acting differently around you to the norm we had. No guy likes it when his woman shows disrepect for him. (now that's just a scenario - it may or may not have happened that way)
You also note that there are several other factors in wrestling other than strength...so while you phrase it as a strength issue - it's the fact that your son apparently won with 'strength' that has you upset.
So why do you need validation from others regarding your feelings on this matter?