Appreciating Diversity
Have you ever been to the woods or forest? Notice that you will never see only plants of the same type together. There are always different types of plants growing together.

Even in our city, we cannot survive unless we have different people doing different jobs - sanitation engineers, baker, butcher, police etc. Imagine if everyone is a baker who will supply the flour? Or everyone is a butcher, who is going to rear the animals for slaughter?
Many modern breakthroughs were only possible when someone challenged the beliefs of the time. Take the airplane - man cannot fly.
Illogical
Even the climate and environment is different when we go to different parts of the world. Despite all this we still see incidents of people trying to make others conform to their beliefs or way of thinking. Hate of people from other religions or races.
Why do countries continue to go to war to force their beliefs on others? Vietnam, Iraq are some recent ones. World War II, Roman conquests are some older ones. Will we never learn from the fallacies of the past?
We claim to be civilized and yet we continue to hold on to our barbaric ways of life that causing pain and suffering to others. When can we achieve the Ethiopia envisioned by Gene Roddenberry in Star Trek?