Bad people too. One of my German Shepherds LOVES people. She will go up to pretty much anyone and sit on their feet and expect to be loved on. So when she growled at the first person ever while my wife and I were on a walk with our dogs, I trust that.

Definitely, my old dog rocco mixed rhodesian ridgeback/ Argentinian doggo. Never growled or shown aggression to anyone, untill he met a woman who had been prosecuted for animal cruelly, but still owned cats, she approached him and he lunged at her, very aggressively, i believe ge coukd smell the distressed cats on her.