Maybe someone who has been bitten, or threatened. Maybe someone who is tired of having dog poop in his yard or on his sidewalk.
Not saying it’s ok to injure innocent dogs about it, but people do get fed up. Maybe someone who gets kept awake by them.
If some guy is pissed about dog crap on his lawn (I do too), seems like an awful dumb move to attempt to shut down the dog park. “Well, we can’t go to the dog park, I guess we’ll just walk around the block and he can poop on the lawns.”