It drew attention to a situation; potentially making it less easy for the child’s parents, local law enforcement, and social services to ignore what is going on.
I agree with vetbridge (my hero!) - it appears that there has been a problem with this child being unsupervised for quite some time. The child (fortunately) doesn’t realize he is being insulted, but it pissed off his mother enough for her to call attention to her own lousy parenting skills.
Not the way I would have chosen to handle it, but something had to be done before the child was hurt.