Laws protect us by restraining sin, not by freeing any inner goodness within the human race, for there is none. The Holocaust in Nazi Germany is only one of many proofs of this statement. War and killing are not unnatural to the sinful human race. Violence is THE most natural of all human reactions to any interference with our pride, selfish desires and hair-trigger tempers. Evolution says we fight because of our animal instincts.
Animals do fight and kill each other, but never for mere entertainment.
We buy toy soldiers and toy weapons for our kids. We kill animals for trophies to hang on our walls. A fish doesn't know it's wet. A skunk doesn't know it stinks. A dung beetle doesn't realize that it's eating poop.