How do you protect your child from vicious rumors when the parents of the child spreading the rumors refuse to do anything?

Well sorry but you can't stop rumors about your child. You can tell me that she/he is better than the people spreading the rumors. And if people come up to them and make them feel bad than tell your child to just say "It is none of your buissness." But the best thing is to teach your daughter/son how to deal with these things cause hey can always get worse as they get older