Now that our men had possession of the walls and towers, wonderful sights were to be seen. Some of our men (and this was merciful) cut off the heads of their enemies; others shot them with arrows, so that they fell from the towers; others tortured them longer by casting them into the flames.
Now, who says it's wrong to be unmerciful. Who says you're supposed to love your enemies, anyway?
Well, at least Paul felt that we should be gracious to our enemies (Romans 12:20). BTW, the reference to heaping "burning coals on his head" is often mistaken for allowing your enemy to feel guilty or something similar. Actually, the reference implies giving your enemy the means to cook food and keep warm.