Fairness—or equity—is integral to God’s character and His dealings with humanity.
"With righteousness He shall judge the world, And the peoples with equity." - Psalm 98:9.
If evolution were true, then fairness would not exist as it is based on survival of the fittest, and good moral behaviour only counts as an expedient to 'perpetuate the species’. So the fact that there is a sense of ‘fair play’ points to a higher calling for humanity than just living out animal instincts.
The enemy of God on the other hand is intrinsically unfair. He doesn’t play by the rules. He distorted the Word of God to Adam and Eve. He inspired false accusations against Naboth, John the Baptist, the Apostle Paul and the Lord Jesus. And against William Tyndale and the many saints described in Foxes Book of Martyrs. And against many Christians today accused of hate speech for faithfully testifying to the gospel of salvation from sin through repentance.
There is another dimension to God’s fairness which goes beyond human reasoning. God is more than fair. He gives us salvation we don’t deserve (definition of Grace) and does not give us the judgment we do deserve (definition of Mercy). He receives the prodigal son back home. He pays the worker a full day’s wage when he has only been hired at the end of the day. He credits righteousness apart from works. "Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God." - 1 John 3:1
So, how should we react? Like the unmerciful servant who has been forgiven much but then goes back and throttles someone who owes him little? No, we should adopt God’s measure of fairness. Forgive 70 times 7. Love our enemies. Shout from the rooftops the gospel of salvation. To do any less would not be fair.