Many yrs ago I did a weekend of respite care for one of those type of kids who was about 9 at the time. They truly ARE dangerous. He had no pets at home, (now I know why), and was very Eddie Haskel like, (meant to put you off guard). But we knew he could be very mean, so we supervised constantly, and I mean literally not letting him be in a room alone with one of our kids or pets. But he was very opportunistic, and he nearly crippled our Rottie. On the third and last day Ruby couldn't get off the couch, her back end was paralyzed. We rushed her to the vet and while she ended up being able to walk again, she was never the same. I wondered if it was him, but just couldn't think of a time when he was alone with her. When confronted he bragged, He said he would wait for just the right moment, (such as on the way to bathroom), and step into a room she was sleeping in across the hall really quick and stomp her knees and her back. We never even heard her yelp. He said she just took it the first couple times, then the third time she bared her teeth and growled and he decided that was enough. This was the most gentle dog in the world. But yea, had she bit him, she would have gotten the blame. This is a Ted Bundy in the making....he is now 16 and has let us know we will someday pay for the trouble we caused him....I believe him.
Children learn by example...we as parents must remember that our babies are always watching us and if they see us do something, they automatically feel it is ok.