What part of the story did you not understand? How did a St. Bernard become a pit bull, and how did "The police report in the incident does not list any guns found at the Harris home and no one was arrested" become the home of a drug dealer?
Another distinction... Mailmen aren't armed, they just get bitten or refuse to deliver to an address with a bad dog. The work of a cop is a little different, he's not allowed to just go right on by if it looks dangerous, is he?
So any dog that comes towards you wagging its tail "looks dangerous" now and deserves to be shot on the spot?
The stories you posted to try to prove to me that cops kill dogs all the time, half of those were pit bulls, and were probably not owned by little church ladies with edged yards lined with tulips. I'm gonna guess a look at this place with the St Bernard would be enlightening too.
So any dog that comes towards you wagging its tail "looks dangerous" now and deserves to be shot on the spot?
No. You missed the point. You compared the work of a police officer with that of a mailman. If a mailman or parcel delivery so much as sees a loose dog they don't go to the door, they refuse and leave a note in the mailbox. I don't think cops have the same luxury.