They generally are not drunken idiots ALL the time. They are more likely to be able to be rehab’d into a better person. A genuinely nasty sadistic bastard most likely cannot.
And usually the younger the person is, the more likely they can become a better person. It’s ones that have lived like that 20, 30 years and look like death that are the ones that are pretty much lost.
Never mind that this incident was likely just incidental. The “woman” (should’ve known - “collegiate” teenager, with a mother too young) was clearly combative, apparently beating up on her mother. The dog just got in the way.
Of course, I’m also surmising the possibility that the dog came to defend the mother, and just got bitten before s/he could bite teenage woman.