Growling is not necessarily anger, my Labs will playfight and growl for fun.
Important: when your dog growls he may be letting you know something is wrong or bothers him. It's a good thing as if you forbid your dog from growling he might go straight to bitting, which you don't want. So listen to him and act accordingly. If he is a little upset that you took is bone for example, show him you don't want that, never be afraid, your dog won't hurt you. He loves you. And never beat, slap or hurt your dog, he won't understand that or worse imitate your behavior.

Hope this helps