Stranger shouting at me?

I took my five year old the other day to a haircut. He doesn't feel comfortable with a haircut, but this time it was horrible. He started crying immediately and i was trying to convince him with the promise of lollipop etc. 10 seconds into this, a woman from behind yelled "Stop crying..just shut up.."And everyone in teh salon were shocked, including my son. But within five seconds, he picked up crying again. I did not say a thing then and stopped his haircut and put him on the floor. he was completely frozen. I did not know what to do, and just left the shop. While driving back home, I realized i should have encountered that lady and told her not to yell at kids, particualrly other ones. Granted, its a matter of inconvenience to have a crying child around, but you need to give some time to things to settle. So, I went back to her (this time my son was still in the car) and told her "You should not have yelled at my son. That was none of your business". She started arguing "Ofcourse its my business." I told her "you should have talked to me or the salon specialist about it or be polite, not yell at my son". she started then telling "Your son looks like he is five. He needs some discipline". At this point a complete stranger who was not there before when the actual event happened shouted at me 'Hey, get out of here..cause no trouble". I was looking at this guy and then this lady said "You Indains dont know how to discipline". At this i said "this is nonsense. It has nothign to do with me being Indian..this is very racist behavior" and then walked out of the salon and the stranger was again looking at me and saying "Get out of here, get out of here". I did not talk to him at all. I anyway got out of there, and while i am glad that i made my point, was unhappy that this stranger interjected and humiliated me. What did i do wrong? How should i have reacted to the whole situation?