Here's the kind of situation where the philosophy of "Bones" applies.
I have a friend with a very tall yellow Lab, he's almost as big as my Dane mix. They are first time dog owners, but really did their homework, went to lots of classes, and he is very well trained (he is now a therapy dog).
Well, she asked for advice about a sudden change in "personality". At first she thought it was her camera, everytime she asked him to sit and pointed the camera at him, he got up. When she went to put him back in the sit he refused, and when she tried to force him he growled (throaty growl with no teeth). The next day he again refused the sit, and growled at her husband when he tried to make him. He did lay down, but continued to refuse the sit command, or layed down instead.
Everyone insisted the dog was "testing" them, and recommended NILIF and other "alpha reinforcing" techniques. Most people said that growling is NEVER acceptable, and that the dog needed strong corrections for this behavior.
I know this dog, it was really out of character for him. Then they posted pics of their recent snowshoe expedition. There was the dog, plowing through some really deep snow. I called her, and we had a discussion about long-legged dogs and the effort involved in walking in snow over their hocks. She took him to the vet, and it turned out he had an inflamed tendon! It was very sore- that's why he didn't want to sit, and he was growling to try to tell them that forcing him was hurting bad.
I NEVER "correct first and ask questions later" I have always tried to figure out where the behavior comes from and what the dog is trying to tell me.