The biggest problem is Religion. People will keep saying they are right with zero basis, citing materials that have zero basis. Result? No unity, because there's no search for a single truth. Truth that is offered by science.

Example: Muslims enraged by purported flushing of the Koran. Yet, you do not see the same riots and outrage when peoples' heads are being beheaded on camera.

Division on religion.

If you take out religion from the equation, people will be more reasonable. Because they cannot, ever invoke "God" which is not proven in the first and not supported by any scientific reasoning.