how to protect ur child from rude people?

My Child was playing on the slide today,she was waiting for her turn the girl infront of her was siitting on n not sliding ,so my dauther start to push her and then I told my kid in my language that you should stop doing it,when I was talking to my kid this lady maybe polish lady(the mother of that girl),start pointing her finger n saying no kicking or pushing.I guess when I was there she had no right to talk to my kid like that.Just was so shocked with such a rude person could not show any reaction and now I am all feeling guilty for my child.