when a stranger tough and kiss a baby...how to react with them?what to say to those people?

A. hi well , saying no directly can be like you feel that person insulted so instead of it , you can keep your child with you whenever you meet strangers try to divert them by talking with them or you can tell that a child might cry or child is ill etc , such things are not right but sometimes because of our child Health or well being ,we need to do this