I suspect most of the outcry is down to people feeling a bit squeamish about the somewhat grisly way it was done.
If a car had accidentally hit the dog and flattened it while running loose, no story.
If the police had shot or stunned the dog, no story.
As noted, dynamic assessment made and, while not elegant or pleasant, incident resolved.
With regard to swerving, I hit a pheasant on the M4 several years ago, after it waddled out into the inside lane at point blank range. Something stopped me from instinctively swerving, maybe it was recalling from years earlier what a driving instructor told me while learning, "If you swerve at that speed (40 MPH) you will roll the car over."
Took out the front number-plate though, the radiator was covered in feathers and red mush and for about a month after once the engine and exhaust got warm, all you could smell was burnt bird and feathers.