When I was a kid, seemed like my mother was always telling me to chew my food instead of swallowing it whole. I still hear parents using the same line on their children, so I guess it must have some value to have survived for so long. Strikes me, that might be really good advice for modern-day pet owners.
When I began seriously to breed and train dogs, I could locate only a very few books dealing with either training or breeding. Today there is so much information available about dogs that no-one could possibly read all of it, let alone digest it all and apply it to their own pets. Much of this information is good advice, given freely, in hopes of helping less experienced pet owners get more enjoyment from their dogs. Much more of the information is absurd, useless, counter-productive, and sometimes absolutely destructive.
People selling everything from flea soap to emergency medical treatment are trying to make a buck in the pet industry. Dog food companies have a vested interest in promoting 'complete and balanced' or 'gourmet' rations. Manufacturers of vaccines have a vested interest in promoting 'disease protection through regular vaccination' of your pet. And yes, even your vet has to make ends meet. ( I suspect my own vet has to conjure up visions of steak on the barbeque to help her put up with me. :)
Authors of books and articles about dogs write in the hope of realizing a profit from their sale. 'Rising-star' trainers who may wish to become the latest 'guru' in the doggy-world need to find a new 'hook'. Obedience classes survive only if they can enroll sufficient new students. Web sites in abundance exist to sell everything from toys to pet safety harnesses. (with the exception, of course of this site) :). All of the above have a vested interest in not offending the tender-hearted ladies and gents of dogdom.
The fact that people are trying to make a buck doesn't mean that they are dishonest or that the information they dispense is incorrect. Many of these people provide invaluable service to pet owners. Some give advice that may be valid for certain breeds, or individual dogs and invalid for others. Some give advice that could hardly be helpful under any circumstances.
In dealing with the information-overload today's pet owners are subjected to it might be wise to keep an open mind, view everything with a jaundiced eye, ( yes that includes this site! ) and like your momma told ya ... "Chew well before swallowing".
Good luck with your training!
Neil