i agree gbailey, you did an amazing job.
i think that your friend bringing it up was good also. sometimes as a parent we don't always see what our child is doing, OR see what they are doing is hurtful, especially when they are so young.
although i don't expect someone to stop mid reprimand to say something to my kid, IF they saw something at that moment and didn't like it, and i was not witnessing it, they could easily say something like "I am handling this, thanks xxx" i have done that and it never bothered me to do it , nor did it seem to upset that other parents. sometimes i think we as parents get over sensitive, and sort of over think things, make mountains out of mole hills.
all someone needs to do is point out their need, otherwise how on earth are you suppose to know. you friend did that, you listened and it made all the difference.
just like if something doesn't bother you, how are you suppose to know that someone else is bothered by it, unless they say something.