Luckily it is no longer considered appropriate in our society
Oh, but sadly, it is considered very appropriate. In many, many segments of our sociey, dogs are still routinely taken out back and shot, or put in a bag and drowned. Stray dogs can be legally and routinely shot if found wandering in rural areas. Dogs are regularly killed for not being a good enough working dog, or for going after livestock, poultry, or other dogs. Many, many breeders still cull out-of-standards pups, and many dog circles see nothing wrong with this. Call it "culling" or simply "killing", but it happens all over, every day.

And, foremost, tens of thousands of dogs are "culled" at shelters and humane socities and animal controls each and every day, all over the world. We as a society see nothing wrong with killing the extras, the leftovers, the homeless every day ... out of sight, out of mind. And a major contributor to pet overpopulation is BYB's and puppymills ... which brings me around again to my original comments concerning BYB's, puppymills, and "teacups" ....