The argument is whether a child who is entering a country illegally can be an exception from law? If the answer is yes then we have several problems. First, in future any kids could enter USA without a permission. Second, should children take the responsibility by law for what they did? What about if they are committed in serious crimes? 

In law, everyone must be equal! We call it justice. No one is above the law. The kids can not be above the law neither. You can not say they are children or minors and they do not know anything about the rules so the immigration law does not apply to them. It just doesn’t make sense.