Why is there such resistance to this? Some people act as if they have never heard of such a thing before. I guess it's because we have grown accustomed to talking about people "becoming Christians" when they are older and have conversion experiences. A baptized child then "becomes a Christian" when he gets old enough to pray a certain prayer or experience the guilt of sin and the forgiveness of Christ in a more mature way. If this is how one "becomes a Christian" how can we considered little children "Christians" before they have had such an experience? You see the problem.
But this is not really the best way to put it. I'm all for conversion experiences. Our Christian children need to experience the power and guilt of sin in order to appreciate the forgiveness of God. But when a baptized Christian child experiences in a fresh, mature way God's mercy and grace in high school or college they have not "become a Christian." They are growing and learning truths about themselves and God that they couldn't learn as little children. That's great. It's absolutely needful. But let's stop telling them that they weren't Christians before those experiences. That's just not accurate.
A baptized infant bears the name of Christ. God graciously gives him a new name. He is baptized into the name of Father, Son, and Holy Spirit. The child is thereby baptized into the body of Christ and becomes a member of the church. Baptized children don't "join the church" later on when they are older. Their formal admission into the membership of the church is by baptism. And if they are members of the church, they are Christians. How could it be otherwise?
But someone might ask,"But are they truly Christians? Are they really, genuinely Christians?" And by this they no doubt are asking if this particular baptized child is regenerate and one of the elect? But this same question can be asked of any member of the church, child or adult. There are all sorts of people who pray the sinners prayer, have singular conversion experiences, profess faith in Christ, etc. They don't all turn out to be "real, true Christians," do they?
You see, this way of using the designation "Christian" is really not very helpful at all. If we are talking about inward regeneration and a true change of heart, how can anyone know for certain who is a "true Christian." We can't. We don't deal directly with other people's hearts and souls. We relate to each other through words and actions and ritual signs.
And why do we deny to little children genuine spirituality? Why can't little children have a faith appropriate to their age? Why must all professions of faith by little children be regarded with such suspicion? Why is it more real for an adult to say, "I believe," than for a little child? I seem to recall Jesus making the faith of little children paradigmatic for adults! We have reversed it.
Baptized children are Christians. We ought to relate to them as such. We pray that they grow up to be faithful Christians. This is the proper qualifying adjective. There are lots of Christians who are not faithful to their calling in baptism. Some even must be cut off from the body of Christ and lose the privilege of being called "Christian." All of us are inconsistent and fail to live up to the name we were given at Baptism. Even so, at Baptism infant children receive the name "Christian."
Here's a helpful portion of the Second Helvetic (Swiss) Reformed confession (A.D 1566) on Baptism:
WHAT IT MEANS TO BE BAPTIZED. Now to be baptized in the name of Christ is to be enrolled, entered, and received into the covenant and family, and so into the inheritance of the sons of God; yes, and in this life to be called after the name of God; that is to say, to be called a son of God; to be cleansed also from the filthiness of sins, and to be granted the manifold grace of God, in order to lead a new and innocent life. Baptism, therefore, calls to mind and renews the great favor God has shown to the race of mortal men. For we are all born in the pollution of sin and are the children of wrath. But God, who is rich in mercy, freely cleanses us from our sins by the blood of his Son, and in him adopts us to be his sons, and by a holy covenant joins us to himself, and enriches us with various gifts, that we might live a new life. All these things are assured by baptism. For inwardly we are regenerated, purified, and renewed by God through the Holy Spirit and outwardly we receive the assurance of the greatest gifts in the water, by which also those great benefits are represented, and, as it were, set before our eyes to be beheld.