Your child is describing a difficult subjective experience but it is important to keep in mind that this is sadly the case for many kids nowadays. We first want to praise you for the fact that he felt comfortable coming to you and sharing his plight with you. It's important that you continue to talk to him about his online conduct and attempt to map out "flow charts" of his online conversations along with him. That way you can more deeply understand what he is experiencing and attempt to help him avoid situations where he becomes vulnerable to his friends. We wouldn't recommend directly intervening or going to other parents unless the remarks against him are abusive, and would instead work with him on reinforcements and avoidance of "volatile" situations.
We would certainly involve the school counselor and the homeroom teacher, asking them not to directly discuss the child's experience, but rather to hold an open, guided discussion about social media use in class. In any case this sounds like a good time to consult a professional about social media use by the family as a whole. Click here to schedule a consultation meeting with ParaNet.