to continue what Erik said:
Check the history books. Killing and violence have never been a difficult thing for humans.
Actually you are very wrong in this case. As a member of the U.S. Army Rangers I can tell you first hand that killing is very much so a difficult thing for anyone to do. In fact humans have such a revulsion to killing another human being that throughout history getting them (the soliders) to fire on the enemy was quite a difficult task, the fire rates of WWII was about 10-20% of soliders that would do so. Through operant conditioning this has been raised to about 90% during the Vietnam era. This is not to say our fathers and Grandfathers were cowards, they would easily risk thier life to rescue wounded soldiers, deliver messages and ammo, resupply other soliders, this was not just an american phenomenon, this is cross-cultural as well. Studies have shown, that that 10% who actually did partake in the killing were psychologically predispostioned towards that kind of violence. mankind should not cringe at this statistic they should be proud that we do have this respect for life. History way show that we have long been engaged in warfare, but this warfare is not fought by the men and women who start them. and whose aims they are fighting for, they are fought by the men and women who take no pride or pleasure in the very situation that they find themselves in.