They call my mixed son "nigg"

Ok so I'm pissed right now. I have a 2 year old that is mixed. His father is African American. He is not very involved but i let him have pictures and he shares them in his Facebook page. he doesnt ask for the pictures he just takes them from my Facebook and makes it seem like he is more involved than he is. His friends and family are commenting calling him their "lil nigg" and racial things using the N word. They are also white. I'm not ok with this and I feel like its absolutely inappropriate. Is it petty if I stop letting him have access to my Facebook page to have these pictures? He captions them saying "my little mini loves his dinner" and things like that when he sees him MAYBE 3 times a year. Am I overreacting or is this just wrong?