I don’t think he was being a douche (and no, I don’t do this, I live on a railroad, and enjoy all sort of wildlife, and it all taunts my dog :)).
It is a great tactic, and it was good he was recording as well. Why should a person respecting the rules always be at the disadvantage of the violator, if there are simple solutions that don’t impact anyone else’s rights?
Now if she allowed the dog to take the treat, and the dog died, and it turned out the treat was poisoned, then yeah, criminal douche in that case.
But that was nothing like what happened.