People get upset when their dogs growl - especially when the dog is growling at THEM!
There’s an old, outdated idea that the human has to be the “alpha,” and any growling or barking means a challenge to authority and pack leadership.
But really, growling can be a dog's way of communicating with us. The only verbal ways that they can communicate are barking, growling or howling. The growling might mean, “This really stresses me out Boss, can you get me out of here?” It can mean, “I’m really not having a good day. My stomach is upset, my leg hurts - can you give me some space?” It can mean, “Dude, the last time somebody got near my food bowl, it got taken away.” It can even mean, “Get out of my face. Now.”
Sometimes growling is a communication, and sometimes it is a reaction, but I would rather have a dog talk to me with a growl, than just bite without warning (and that happens). And figuring out why the dog is growling can only help your relationship with the dog, because you get to learn more about your dog’s personality, and how he/she thinks, feels and learns.
Listen to your dog. Watch your dog’s body language - ears going forward or back, stiff or tucked tail, hard stare, moon eyes (seeing a crescent moon in the whites of the eyes) - when interacting with you, and with other people or animals. Understanding why your dog growls can help us change the way the dog feels about a stressful stimulus, and make the dog feel better. The more we understand our dog friends and the way they communicate, the more we can love them and help them.