With the exception of the person questioning whether the world would end in 2012, there seems to be a universal theme throughout the answers: people. Without people, none of these issues would have come about. Sadly, the only solution to that would be the elimination of the problem. Of course, if people are removed from the earth, there would be no one to enjoy the problem-free world.
A second, and less bleak, solution would be to have everyone get along. That, my friend, is simply impossible. The only way to have that come around is for everyone to think alike. I truly don't think that Pol Pot, Joseph Stalin, Idi Amin Dada, Caligula, or any one else could simply be sat down and talked into doing what you felt was best. Just look at the U.S. alone. Do you really think that there will be a day when every politician sees eye to eye on every issue?
Simply put, as strongly as you feel about something, there is likely someone who feels just as strongly in opposition. There is just as much chance as you taking their side on the issue as there is of them taking yours. I doubt Bin Laden could talk you into thinking what he did was right, just as I doubt you could talk him into thinking the opposite.
Every problem in the world is either created or perceived by man. Without the creator or the perceiver, there would be no problems, and no one to realize the lack of them.