Hmm, that's a very good point, that speaking of the mistake by the dog (which the dog didn't have any way of knowing better) in the factual description is separate from assigning the fault. I concede the point and agree that the dog is never at fault in an accident.

The only argument I have remaining is that while it's an incorrect statement, I don't think saying the dog is at fault in an accident is insulting, because being at fault in an accident is often only an honest mistake (albeit sometimes with tragic consequences).