Rom_5:13 (For until the law sin was in the world: but sin is not imputed when there is no law.
The point is: if you (or a baby) has no knowledge of the law (or natural law) there is no sin accounted to you (or a baby)...
Sprinkling a baby will do no more for the baby that it will do for your petunias when you sprinkle them...Actually the petunias will benefit more...
Sprinkling a baby will do no more for its soul than sprinkling an avowed muzlim, or hindu...
No one gets saved in the bible except that they first turn to Jesus, whether they get water baptized or not...
But this point ignores the problem: the sin and death that has passed on all men, including babies who perish.
As for baptism-- we do not believe in baptismal regeneration. The point of baptism is that children, who are not free from sin, and are not free from faith either (like John the Baptist in the womb!), are just as worthy of baptism and into the full life of the church and all its privileges as anyone else. It is not true that there is an "age of accountability," or that confessional baptism is superior, because as valid members of the church (for Peter says that the promise is to us AND our children in Acts), they should not be restrained from receiving its rights.