Those fantasies, while exemplary, are unworthy. So long as people exist there will not be peace in the world.
Through the history of humankind there hasn't been peace in the world. Cavemen fought other cavemen over land, food as well as women. America fought the Revolutionary War for liberty and brother fought brother at our Civil War to get much more liberty. There have always been wars and there'll always be wars.
So long as people can think, there'll be wars. Wars over such notions as liberty, honor, dignity, etc.. Wars over land, greed, power, bias, etc.. War is part of human character. By way of instance, each human being is prejudiced. Should they don't enjoy any race, nationality or faith, they don't enjoy tall or short or fat or skinny or smart or not intelligent or loud or silent men and women. Many people today don't enjoy kids, some people today don't like older folks, some people today don't enjoy folks with pets, or even people who play their music too loud, or even poor drivers, or even people who believe in God or even people who don't believe in God. What's appropriate and appropriate to a folks can be incorrect or even enraging to additional men and women.
Religion can't stop wars, actually many wars have been fought over religion (Note: I feel that faith is used as a justification for war not the actual reason for war) . The Catholic Church murdered heretics during the Inquisition. The Nazis murdered millions of Jews and started killing Catholics. The Russians under Stalin murdered anyone even remotly spiritual. Protestants murdered other Protestants to be the wrong kind of Protestant. Muslims murdered Muslims to be the wrong kind of Muslim. Don't forget about Atheists (I feel that Atheism is also a faith, it's a faith of non belief) , Stalin was an Atheist and wished to eliminate all faith. History is rife with a variety of kinds of religious conflicts.
The most important reason for warfare, however, is that the lust for power. The capability to make others do and think as you do and think, the capability to make different men and women render unto you everything you think is yours, the capability to make different men and women treat you while you think you ought to be medicated, the capability to get what you need (ie: cash, love, esteem, etc.), the ability to punish others for doing things you simply don 't believe they need to do, the capability to prevent other from getting thoughts or things that you simply don 't need. To put it differently, the ability to be, in certain ways God, to make everybody else on your picture with you personally as their ruler.
Provided that individuals have the capability to think, there'll be greed, jealousy, anger and prejudice. Provided that those items exist, there'll be wars. Many people today think, either religiously or secularly, at the principles set down at the Ten Commandments, however, very few people are able to stick to these principles each the time since our capacity to believe causes us to desire. Needing induces us to violate some or all the rules. People aren't perfect. If they had been they wouldn't be human.