BMGGuy
This kid is 100% correct. His mitzvah of הוכח תוכיח might be characterized as based on חינוך. You might have an issue if he screamed it and caused the fellow embarrassment – really untactful. Meanwhile, if someone hears something that is in the direction of mussar, he needs to accept it whether it comes from a child, a goy, from random occurrences, or someone who is a בר חיובא in the mitzvah of תוכחה. Failing to heed the message is, in itself, an עברה. Why are you busy defending the בזיון to the בית הכנסת and the ציבור?