I wonder if it's not the CAMERA that gets the dog going.
My brother used to have a dog that was wonderful, UNTIL someone pulled a camera out. Then he would go ballistic, growling, etc. He HATED cameras. We never did figure out why.
And there was an episode of the {Shhh–-} Dog Whisperer once where a dog got really nutso when the family pulled out their video camera. Made filming the episode interesting, but in the end the dog learned the camera was harmless.
AND, camera aside, this is what Keoki used to do when anyone, then finally it got down to just dh, approached when he was resting. We just kept on - talking to him, petting him, telling him "no" when the growling got too intense, etc. and now he seldom even growls at dh.