Dealing with mean toddlers

Hello! I have a three year old boy. We have a few neighbors that have boys with similar age. My son is the youngest. Recently one of the kids has been acting a little mean to my son when they are all playing together. He will push him away, tries to kick him, tries to spit on him and say things like you're not my friend or you are a cry baby. I get that this is kids play but he is only doing it to my son. This also happens in front of the boys parents and they don't say anything. Our approach has been to try and distract our son away from the situation. When my son has tried similar things we've tried to correct it using phrases like "hitting is not nice". I am very conflicted on how to deal with this situation. Its hard to tell my son not to do something when he sees other kids doing it to him and not being corrected. I am also uncomfortable correcting other kids, especially when the parents are around. Does anyone have any advice for me as a parent? Am I over-reacting? Is this normal? Any advice on how I should help my son deal with this situation? Thank you! via /r/Parenting http://ift.tt/2mC8O3l