I own a red-haired Golden - colour my perception, I guess.
She would run up to a stranger like that, and -*ahem*- service them.
On the other hand, my Akita (sadly deceased), would have NEVER run up to someone like that. He would have posted, hackles raised, and sounded a warning.
Now, many years ago, I owned a blue-eyed Alaskan - she would not have offered any warning at all. If she decided something needed to die, it did.
But she also never charged anything in the driveway.
My point is, a charging dog inten on mayhem is not competent to the job - most charging dogs are intent on a but-sniffing lick-fest.
Most definitely. Dogs that would just charge and attack someone are rare, especially when that person doesn't turn and run, which is why the guy slowly backing up makes sense.
Of course in that normal situation where the dog is being really friendly most all people, including most all police officers will recognize that fact.
So this is either the really, really rare dog that attacks, or the really, really rare police officer that shoots the dog that is just being friendly. The consequences of having to deal with the dog owner and fill out lots of paperwork for discharging his weapon is enough to discourage even the bad cops that are indifferent to killing someone's pet.
Without better video or knowing more about the character of the officer, I don't see how there's enough information to really tell one way or the other.