Young children all respond to some form of the Word of God that speaks of God’s innocence, but in addition to a unique Word of God that speaks of the perfect idea God has of that child. When Jesus chastises in His harshest language the one who first scandalizes a child, it is the second Word He has in focus.
Spiritual innocence is a precious and life-giving thing, but, like mother’s milk, it’s meant for a season. It’s an innocence of understanding and, except for the precious few or for those who depart early for heaven, as experience and the understanding of it grows spiritual innocence fades in proportion. This is one of the laws of spiritual nature.
But the Word of God spoken uniquely and privately to each child is that child’s most precious inheritance, and the one who steals from it both reduces the child and devastates the Father. Hence Jesus’ condemnation.