Growling isn't as simple as it seems, and sometimes it's entirely appropriate.
A few days ago Italian dog trainer Debora Segna contacted me about a Facebook posting by veterinarian and philosopher Dr. Roberto Marchesini in which he wrote, “If my dog would growl at me during an interaction, not a playful growl during a playing interaction, but a warning and threatening growl, I would question the relationship I have built. For me it wouldn't be a simple demand, but rather my failure. Obviously I am not talking about adopted adult dogs, with several problems you need to work on. In my life I have had countless dogs and the ones I had since when they were puppies never growled at me. The ones I get from shelters sometimes did in the first times but eventually gave up.
via Whisker Therapy