Working terriers are small dogs and they are commonly pulled from den holes by their tails, and lifted up by the scruff of their neck.
Whenever I see or hear anyone expresses shock at this, they have told me two things: they do not know much about small dogs, and they are not watching the dog that is right in front of their eyes.
This last point is important, as a terrier properly lifted by the thick skin on the back of his or her neck does not yowl or struggle, nor are they prone to wiggle away and jump off.
A scruffed terrier simply relaxes as their small canine bodies have been programmed to do for more than ten thousand years.
This phenomenon even has a name -- it's called clipnosis -- and there have been scientific papers written about its effectiveness on dogs, cats, and other animals.
Clipnosis, or "pinch-induced behavioral inhibition" responses, have been seen in a wide range of animals, including mice, rats, rabbits, dogs, and guinea pigs.
If you go to Google Scholar and search for "dorsal immobility" or "transport immobility," you will find a few hundred studies going back several decades.
In the modern pet world, the phenomenon is most commonly done with cats, with 2-inch binder clips creating the "pinch-induced behavioral inhibition" (see the video, below). Amazon even sells a Clipnosis Gentle Calming Cat Clip which looks suspiciously like a woman's hair clip.
Are there limits as to weight when it comes to scruffing?
Sure. I would not do it for a dog that weighed more than 25 pounds or so, but working terriers are about half that weight, and scruffing has been a traditional way of pulling terriers and fox out of holes in order to maintain maximum control and minimize struggle or fuss for hundreds of years.
To be clear -- the dog is not scruffed for a long period of time -- less than 5 seconds is typical, as seen in the video at top which is from a TV newscast detailing the recent flooding in Baton Rouge.
Whenever someone hyperventilates about it being "disrespectful" to scruff a fox, cat, or small dog I know two things: 1) they still think dogs and cats are about how they feel and what they think, and; 2) they are not being very observant.
Here's a clue: Dogs have a useful code inside them, and using that code to help either dog or man is never wrong.