A good dogman can take a dog with alot of potential and with a little luck turn the dog into something special to watch. If the dog has no potential it wont matter what they do, they will still be feeding a cull. As far as ruining dogs with alot of potential, its very very rare. It is so rare that its not even worth mentioning. I've met very few men with balls big enough to "ruin a good un". What I mean by that is most people I have met are very soft both inside and out and they will make excuse after excuse instead of puttin the time and effort into finding out what they truthfully have