If I became a professional handler in AKC...?

If I become a professional handler in AKC (I'm still a junior right now), would it be wrong to refuse to show a dog because of the way it's made? For example, I would refuse to show an American Bred German Shepherd, but I would be okay with showing a Czech/working line GSD (obviously that would never happen, just using it as an example)? Or, refusing to show a Border Collie or Aussie that could never work simply because it has too much coat and bone? Those are examples of dogs that finish very easily in AKC, but I would really only handle dogs I believed were made good enough to withstand the job they were bred for.