Read the Old Testament. God actually commanded the genocide of several nations. Also, Ecclesiastes 3:1-8
For everything there is a season, and a time for every matter under heaven:
2 a time to be born, and a time to die;
a time to plant, and a time to pluck up what is planted;
3 a time to
kill, and a time to heal;
a time to break down, and a time to build up;
4 a time to weep, and a time to laugh;
a time to mourn, and a time to dance;
5 a time to cast away stones, and a time to gather stones together;
a time to embrace, and a time to refrain from embracing;
6 a time to seek, and a time to lose;
a time to keep, and a time to cast away;
7 a time to tear, and a time to sew;
a time to keep silence, and a time to speak;
8 a time to love, and a time to
hate;
a time for
war, and a time for peace.
Not quite as Kumbaya as you thought, huh?