An abortion doctor shot dead in his church.
An American soldier shot dead on the sidewalk outside a recruitment office.
A security guard shot dead keeping watch at the national holocaust museum.
What do all three have in common? They were motivated by anger turned to hatred turned to vengeance. None of the three can be said to be rational. But then human vengeance is seldom, if ever, rational.
Vengeance is irrational because knowledge is limited and emotions cannot be trusted. Such a combination often leads to wrong initial conclusions and can lead to regretted acts. This is why vengeance is kept in the purview of God.
Romans 12:19 – Beloved, do not avenge yourselves, but rather give place to wrath; for it is written, "Vengeance is Mine, I will repay," says the Lord.
God's knowledge is not limited. He knows the truth about everything. And God's emotions do not cloud His judgment. He sees perfectly not only the act committed but also the heart of the one committing the act.
This is also why God instituted government. (Romans 13:1-5) When law enforcement and the judicial system function as God ordained them to function, vengeance is averted and justice is served. When the system does not function as Divinely designed, we, as Christians, still trust in the justice of God, Himself.
Trusting in the ultimate justice of God frees us to live vengeful-free lives. In fact, it allows us to live lives loving our enemies and overcoming evil with good. Don't take my word for it. Listen to the Holy Spirit inspired words of Paul the Apostle to the church at Rome.
Romans 12:17-21 – Repay no one evil for evil. Have regard for good things in the sight of all men. If it is possible, as much as depends on you, live peaceably with all men. Beloved, do not avenge yourselves, but rather give place to wrath; for it is written, "Vengeance is Mine, I will repay," says the Lord. Therefore "If your enemy is hungry, feed him; If he is thirsty, give him a drink; For in so doing you will heap coals of fire on his head." Do not be overcome by evil, but overcome evil with good.