This is a common problem."my son would never do that".
We had an issue here with a couple kids that don't like my boys, for of all things, being in the Cadets. It started when my boys went door to door selling raffle tickets, in uniform. The were hounded with names like "Baby, baby killers", "Wannabe soldiers", and so on. They ignored the insults. That only led to vandalism. I caught them one night, went to their house and confronted their parents.
I was flat out told I was lying, their boys had been home all night and that their boys were not that kind of child.
Two later I caught them on one of my trailcams, red handed. I again went to their parents. Again I was told the same thing. Then I presented the pictures. I photoshopped them...
Some people have no clue, and some people wonder why I have so little respect for clueless people?