Kids are, indeed, excessively cruel and I feel his pain as I was subjected to many instances of bullying due to my being very short. I too adopted a 'turn the other cheek' approach although this was mostly for self preservation.
Later though, as I outgrew most of my antagonists, I discovered they were now fearful of my righteous retribution. A glower or a softly, yet deliberately spoken word usually elicited the desired submission of will.
On a lighter note, perhaps the suffering could have been considerably reduced had you not called your child "
C***