<human>: My best friend in the world beats his dog.  The dog is a Bluenose Pit and very stubborn and willful, as some breeds often can be, but I cannot abide by his treatment of the animal when it does make a mess or get out of control.  

I have witnessed it only once myself, when the dog pooped the carpet in the morning and then wouldn't heel to him.  The animal was cowering, and he picked it up by the scruff (too old and heavy to do that) and slammed its haunches onto the ground, yelling at it for being a 'BAD DOG'.  Then, as the dog tried to scurry away he kicked it, hard in the gut.  The dog yelped in pain, and I yelled at him to stop it immediately.

We got into a fight about disciplining the animal, and although I conceded it was not my dog to raise, I asked him to never raise a hand to it again when I am around.  I won't stand for it.

The problem I have is when I am not around, I know that the dog will be beat.  I believe in Corporal Discipline for tough dogs, like a good whack on the nose and firm 'NO!', etc...but not this.  What should I do?  Do I report it to the authorities?  I don't want him to get in trouble, he is a generally good guy, my best friend, and already has had issues with the law in his youth.

Summarize the given text in a few sentences.
<bot>: My best friend in the whole world beats his stubborn dog when regular discipline fails, and I have asked him to never do it in my presence.  What else should I do?