You should not believe everything everyone says, just because it outrages you. They might be exploiting you.
One of the things I do a lot is observe people, because it helps me understand them better. I have noticed that when someone cries victim, they are granted the benefit of doubt pretty much almost always, and the person they are accusing is assumed to be guilty, even if there isn't any real evidence. The accusation is enough, and the first person to do it is assumed to be truthful. And after that close inspection of the actual facts usually does not happen.
The thing is, there are plenty of people who abuse that tendency in human nature to their own ends. You always need to be wary of that, NEVER believe someone just because they say so. You need corroboration, and in this case there is apparently none.
Now, if this kid had been causing problems in the neighborhood, no one will dare complain about it in the future, because if they do they will be branded as the "letter writer". If you were the parent of a troublesome child, that is a valuable card to be holding.
If you can't see why someone might find that an attractive option, I have a few bridges I'm sure you would be very interested in buying

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