In "God's Word for Today", Steve Oliver writes:
Think back to when your children were small — or, for that matter, not so small. Did you ever hear, “That's not fair!”? What was the real problem that the child was protesting? Usually, it did not have anything to do with real fairness or justice. Rather, the problem was that the child didn't get what he or she wanted. Like children, adults tend to think of justice as “I get what I want” rather than what I actually deserve, but sometimes justice dictates that I get precisely what I do not want. Since God is just, He will always act in a just way, and justice includes giving punishment when it is deserved. In fact, when Christ took our sins, He had to endure the full weight of punishment for them.
Source: Christ, the Triumphant Lord: Adult Teacher's Insights, page 40.