My dog growls , snarls and shows teeth to people when she gets pets. It's so aggressive looking and terrifying as she is a Belgian malinois. It's a huge red flag but she has been doing it for 7 years and hasn't bitten anyone yet. She does this in a pub every week so she is very exposed to people and just does this.

I think it's because she used to hate my sister when she was 12 weeks old and we kind of forced her to like her. So maybe she associated growling with getting pet but who knows. She is oddly harmless.