If the dog is out chasing then we already have a problem because the owners do not have proper control of the animal. It is good that Animal Control can use their judgment to decide if the animal poses a real risk to others in the community before something more serious occurs. An animal need not be "aggressive" in order to pose a real risk to runners, children, cyclists, and cars.

Maybe it's heartless, but I have seen far too many animals that show control problems and risky behavior and the owners are oblivious.

EDIT: I have also seen far too many people who know their animals are aggressive and believe that they can control those impulses.