Why is Infant Baptism considered to be invalid by so many Protestant denominations? Catholics and several Protestant denominations (and maybe even Orthodox churches) practice Infant Baptism, while many other Protestant denominations do not.

This question addressed the argument for Infant Baptism.  So, what is the argument against it?  That is, "Why is Infant Baptism considered to be invalid by many denominations?
In order to be saved, one must follow the order of salvation that the scriptures set forward. Romans 10:14 tells us that the order is 1) preach, 2) hear, 3) believe, and 4) call upon the name of the Lord (baptism, Acts 22:16). Acts 2:38 tells us that repentance comes before baptism, and Romans 10:10 tells us that confession comes after belief.

But let's look at this logically. How could one believe something that they can not understand or even know about? That does not make any sense. That is the reason.

Many other denominations use infant baptism for the parent's benefit. It is a proof that they WILL help their child grow and believe. Then later, in some denominations, the child is re-baptized. 

However, the argument against it is simply because the Bible says you must believe before baptism. Those who hold to this belief will follow this standard, and consider baptism invalid.