The reason that religious teaching that is force on a child is harmful is that it doesn't accept the ability of a child to make up his or her own mind to believe or not. This is
a form of mental abuse. Religious training offers nothing concrete in determining whether behavior will be moral or anti-social. Much of this comes from life's experiences and choices that have little to do with religious dogma. There are plenty of examples of moral and socially-conscious people who help society without being religious.