Police dogs are trained to rat you out, either legitimately or illegitimately.
They don't understand what they're doing. They're not participating in policing. They are being used by cops.
Police horses will do their best to not step on you when forced to ride into a crowd. Not bastard.
That would not be an argument that horse "officers" are not bastards. E.g., lots of human officers drive their cars safely, but that doesn't make them any less bastards.
ACAB because all cops choose to participate in the vile institution of policing. To the best of my knowledge, most non-human animals are cognitively incapable of making that choice. And typically, the "training" to "convince" non-human "officers" to abuse people is itself abusive to the animals.
So, animal "officers" are victims of policing. And they're not bastards because they can't be; they don't have the cognitive functions to intelligently make moral choices. Any monstrous thing an animal "officer" does to any other victims should be considered a crime committed by the animal's human handler and policing as an institution.