I am really sad about this incident, Nadi as a dog it is her nature to be always territorial. Dogs are smart and they can smell, sense or read what was goin on and has an instinct too. That's normal for Nadi to bit him because she saw that asshole wants to touch you. Nadi sense that those gangsters are making bad intensions for you. On the other hand; it was a good thing you have Nadi because it might be worst to what happened if Nadi is not around. I do understand how you feel. Our generation before was teaches to be more respectful, good manners, polite and behaved. Today's generation is very different, not all but mostly so many young people do not have good manners.This is based on my experience. I hope it won't happen again and Nadi would not got trauma from that incident. Wishing you good days with NADI .