The medieval era included many wars fought in the name of a merciful, loving, and gracious God. Many people find this incongruous.
Most humorously the comedy team of Monty Python mocked the use of a "Holy Hand Grenade" during the crusades. The rules for using the hand grenade are found in the "Book of Armaments" (satire of the Bible), which asks God to slaughter the enemy (in Thy mercy).
This incongruity is also apparent in Psalm 137:
Daughter Babylon, doomed to destruction,
happy is the one who repays you
according to what you have done to us.
Happy is the one who seizes your infants and dashes them against the rocks.
DEBATE: Is Christianity compatible with the violent treatment of one's enemies? Can a follower of Jesus sincerely engage in the destruction of human beings, particularly civilians? MLK vs. Abraham Lincoln.