Hitting a special needs person to defend your kid?

If a person with special needs kicked your one year old son would you hit them back? Does it depend if their special needs are physical or mental?

My friends son is one year old and a mentally handicapped member of her family kicked him in the face. Marched up to him and kicked him. Her family member is 30 years old. When her husband saw this he attacked her family member and now her family has cut ties with them.

UPDATE, forgot to mention he has the mental capacity of a 7 year old. And her son is okay but he did have a bloody nose and mouth plus swelling

•The 30 year old man did not kick the baby and just stop or walk away. He showed no sign of stopping and if the father hadn’t intervened the child would have been kicked again