You are entitled to you opinion Dizzy, as Stumpy said. And this is not a personal thing. It's just debating from different points of view. Of course, you're absolutely right that dogs get injured in other ways, ways that can hardly be helped while still letting them be dogs and letting them do what dogs do; run wildly, jump, play roughly, slamming around into things sometimes. Some of the ways dogs get hurt can usually be prevented, as in the case of being hit by cars, a grooming accident or other unnecessary things. But a tail injury is one of the worst because it often results in re-opening of wounds over and over again... and often those wounds are just the type that invite infection, which can be very dangerous and not always responsive to anti biotics. They get gangrene easily and the tissue becomes necrotic. They can actually die from this if not amputated in a timely fashion.
With the type of dogs and type of tails mentioned, when there is available a safe and painless way to prevent that, a procedure that is very minor, it only makes sense to help these dogs in one small way. We can't (or shouldn't) prevent dogs from having fun, running, playing roughly....just being dogs in order to assure no injury whatsoever. That would be cruel. So, if there's a relatively painless or completely painless way which doesn't interfer with their day to day life forever....and there is: docking, then how could anyone possibly deny them or object to that, I don't know.
My Lab wagged her tail furiously. But I never worried. It was what is called an otter tail; thick, heavy, fully covered in fat and loads of hair, which slows the wag down a little. The bone is thick and tough. They're designed to have this protection and this wonderful, full tail to help them swim. They can go through brush and rarely get hurt. But take a dog with a thin, wimpy tail that was designed to be docked and not dock it and there is a moderate risk of injury...and injury that is often ongoing.