In my life I try to live by a motto. I will start condemning others for their mistakes when I stop making them myself. Some people in this life think to much of justice. Justice is important and is an eternal principle but is really a purview of God. Unless we are a part of the earthly justice system we need to focus on mercy. People can't really dispense justice because in order for it to be just it has to take in consideration all factors. As humans we can't know or know how to properly judge all factors. Mercy is easy. It just requires forgiveness. We are just more qualified to dispense mercy than justice.
Let's not forget that the Lord has told us that we will be judges with the judgements that we enforce on others. The woman who was brought before Jesus as an adulteress had men ready to stone her. Jesus said "He that hath no sin, let him cast the first stone." Jesus refused to condemn her, and lot of people seem to think that he forgave her. He did not tell her "Thy sins are forgiven thee" or "Thy faith has made the whole," like he did in other instances. He told her that he was not condemning her at that point in time and then he said. "Go and sin no more. His forgiveness was predicated on her changing her bad behavior.
As parents we need to be kind and merciful to our children, but we can never let the desire to be merciful to harm our kids. If we just allowed our kids to do anything they wanted without consequences, they would not be able to learn to behave correctly. Proper discipline helps our kids and not to mete it where appropriate is a form of neglect. It is a difficult tightrope for us parents to walk, though. How much discipline do we mete out and how much mercy do we show to our kids? It is a fine line, but I believe that if a parent is struggling with this issue, then they are thinking how to discipline their child for the child's sake and not just punishing the child to give themselves an ego boost. If you are doing what you are doing for the benefit of the child than at least you are headed in the right direction.