we can allow each other to have whichever system(s) we wish to, and that way we can have peace.
No, we can't. For example, muslims will never allow polyatheists to exist.
And why do you think that all people want peace?
We can but we won't. That's basically it. If you look at it, it's really up to people to learn how to respect differences whether it's religion or race or culture. I just don't understand why many of us restrict ourselves from realizing that and think they're superior than others