There are so many ways we could go with this...
What was his penis doing in the dogs mouth in the first place? The sick bastard got what was coming to him.
True, and I choose to go this way.....
The dog is a sub-breed of the Pit Bull known as a Bitpenis Bull.
What would you expect?
Reminds of that scene from the movie, “Deuce Bigalow: European Gigolo” when a cat attacks.
https://www.youtube.com/watch?v=SU5GEWWpWdw
(don’t watch if you are easily offended!)