re: Michigan court rules okay for police to kill your dog

The court there is being consistent with a strict liability tort standard for the dog owners in this case. Any owner of a wild animal or domesticated animal with vicious propensity will generally be held to the same standard. I have not read the actual opinion yet but I'm willing to wager that is what you will find in the ruling.

ETA:

The court did and agreed with the policy of the agency involved by citing their policy:

Dangerous Animal, defined: An animal that bites or attacks a person or another animal.

Vicious Dog, defined: An animal of the Canis familaris species which, when either unmuzzled or unleashed, or when not confined to the premises of the owner, menaces a person in a manner which an ordinary and reasonable person would conclude to be an apparent attitude of attack.