This is an important question. Emotional abuse towards chidren is extremely hurtful for many reasons. I will mention only two. First children are malleable. In other words, they are still growing and they are learning. So, when people abuse them, it becomes part of who they are. Their self-identity is formed. So, if you call a child fat or give them weight issues, then even if they are not fat as adults, they will think they are. Second, this abuse will have long term effects and when children become adults, they will carry a lot of baggage with them in all that they do. It will effect their quality of life.
As to how we can stop it, there are no easy solutions. First, we should probably start with educating people that verbal abuse is never right. Second, we should personally take steps in loving children. Third, if you know of severe cases, there might have to be external intervention by a social worker.