There is no scripture in the bible that I know of that says that children should by punished for the sins of their parents. If the object of this "rule" is to condemn the act of fornication, then why should children be made to suffer the consequences?
Quite a people that I know and love were born out of wedlock and it didn't make them any different than those who were not. In fact some of them are the most successful, productive members of society. They are managing and have managed to thrive because of their contributions and abilities. Not because of the marital status of their parents.
The church should be a non-judgemental safe haven accepting of all those who enter. Refusing to baptize babies born out of wedlock sends a mixed message. God is accepts all people, unless........