It is an interesting phenomenon, and you're quite right - I've seen the Lab boards where debarking is a flameworthy topic.
My theory is that we've simply reached a critical mass of cultural acceptance: enough breeders have their dogs debarked (and are 100% OK with it) that they tell their puppy-buyers that it's OK, and the puppy-buyers go forth and spread the good news, so to speak. A huge part of that is the process by which debarking becomes 100% acceptable among breeders. Back in the very early 90's, we had a very barky young bitch. She was the first one we had debarked, and it was only after a great deal of consideration.
Now, the reality was that the little dog was quite obviously none the worse for wear after debarking. As an owner, my mother could see that she barked just as much after the surgery as she had before, and seemed to suffer no physical or mental harm as a result.
And that, I think, is the critical tipping point. If you've only ever met one or two debarked dogs, it's very easy to construct a narrative in which the meanie abusive owner has had the poor animal's voice-box removed (or, more fancifully, has slammed a steel pipe down the dog's throat). However, if you meet enough happy, healthy debarked dogs... and enough caring, perfectly-humane owners of debarked dogs... debarking becomes more normalized and more acceptable.
I think that is absolutely what it is, once someone sees that the dog is the same completely happy functioning dog that is was before people go ohhhhh ok I get it! Your not maiming your dog! Only one of mine is de-barked like I said Molly..it was not a snap decision, she was almost 3 when I had her done. It got to the point where I could literally not let her out for more than 2 min to go pee because shed find something to bark at, the birds, a car driving by, someone walking, a dog barking 1/2mile away, a flea jumping..etc you get the idea...
When I went to get my zoning changed my neighbors had no idea I had more than 1 dog..half of them said to me ohhh you have dogs
I think they must be deaf
...but anyways if I can keep them all on that thought of I have no dogs I am not disturbing my neighbors or encroaching upon them with my hobby of the dogs! Its a win win!