It's because everyone thinks their way is superior to others'.

But if everyone's way was peace we couldn't go wrong regardless!

Unless of course one man's definition of peace was world conversion to Christianity, and another's is world conversion to Islam, etc.

The day we have a majority of non theists in the world, and that day is rapidly approaching, there will be a larger chance of world peace.

Don't bet on it.

Peace will come about as a result of the unity of religion.

Anyway, the problem has been when those hungry for power have used religion for their own ends.

Here's some passages from an essay by one of my fellow Baha'is -- which in turn has some quotes from one of the central figures of our faith -- which address that:

"Race is a good example of this feedback loop. We know that race has no reality. But the existence of racist structures and institutions in a society affect its members: people will be shaped by those elements of a society, perceive race, and perpetuate it. But people who want to overcome racism can take deliberate steps to change their own thoughts, to deliberately break down habits of racial separation -- their actions can have an affect on the shape of the society. The effects go both ways.

Another concept to keep in mind is that not all transformations are progressive. A selfish action can have consequences far beyond the intentions of the initiator. In 1914, travelling in the United States, Abdu'l Baha stated that national and racial distinctions were created by despots and conquerors who sought to dominate others:

"We are all human, all servants of God and all come from Adam's family. Why, then, all these fallacious national and racial distinctions? These boundary lines and artificial barriers have been created by despots and conquerors who sought to attain dominion over mankind, thereby engendering patriotic feeling and rousing selfish devotion to merely local standards of government."[3]

Not necessarily. Just a general consensus on tolerance.

And wishing that the majority of the world was non-theist is almost equivalent to the evangelism of religions that believe peace will come when a majority of humanity is converted to their religion. Being that, it still follows the same mode of intolerance. The only intolerance that would work in this context is intolerance for intolerance. In other words, it's more accurate to say that peace is more probable when most of humanity hold each other in tolerance, and not necessarily the same religion.

To be perfectly honest with you, if everyone believed the same thing, that would be very boring and I probably wouldn't want to live in a world like that. However, I think everyone needs to be more tolerant of each other.

I don't believe in everybody converting to the same religion. In fact -- while eventual and true world peace is one central promise of my religion -- it also clearly states that.

A: Not everybody will be Baha'i, nor is everybody supposed to be.
B: ALL peope of good will, not Baha'is alone, will bring about peace and the eventual maturity of the human race.

There is no unity based around a lie. Most of the war's of our world speak to this clearly.

Exactly; humans will never unite around something they can't see and is objectified from practical reality. They will only unite on the basis of humanity and the commonality of the species-being; perhaps realization of our oneness will help. In other words, humans won't unite on the basis of their differences (religions) but on the basis of what they have in common (humanism).