I physically stand between them. I've had to do this at playgroup meetings.

I don't touch the child that's being offensive. I will move between them, even is that means being a bit pushy with my whole body. Once I've done that I look and speak to the one that was hurt or being abused and either guide them away or just wait for the other child to move on. I don't talk about it, I act straight away.

I've had this situation, and it depends on the age of the child. While young children may respond to being told that what they have said or done is hurtful and wrong, teenagers are often beyond that logic. A child learns most of his prejudices before age 5, but even after that, you can reach them.

First, I would come between them and tell the child being harmed to walk away, ask them to go sit somewhere else, perhaps. Then I would tell the offending child that what they did was very wrong, and mean. I would ask them if they enjoyed being mean. Most likely, they will say no. Then you ask them where they heard what they just said or where they learned to do what they did. More than likely, it's from a parent. Ask if you can talk to their parent, and take them to them. Explain in front of the parent exactly what has happened, and ask them politely to please teach their child that it is wrong to be that hateful to another child, no matter their race or ethnicity. Most times, they will be embarrassed enough to apologize. Sometimes parents don't understand that their child learns so much from just watching and listening to them. If they support what their child did, or get belligerent, it's best to just say "I'm so sorry you feel that way. There is too much hatred in the world today, and I'm sorry you choose to teach your child to hate." and walk away.

By saying this in front of the child you are teaching them that hatred is wrong, and maybe they will learn from you. Maybe not, but it's a chance you have to take.