My opinion ....

Bark collars, used properly, are a humane last resort, when training fails.

I have known many people who had two choices with their dog ... stop the barking or euthanise the dog.

We used a bark collar for my husband's dachshund when we first got together. The dog was nine years old and barked constantly ... and I mean that literally. The only time he was not barking was when he was alseep or drinking. He literally barked while eating, while pooping .... seriously. Training had absolutely no impact. I really think he just wasn't quite right in the head, poor guy. But the bark collar worked perfectly.