Hello JM.
People are born human beings, with all that that entails.
Well, this seems to be the crux of the issue. Just what does it entail.
Setting aside that human beings commit rape, murder, cheat and deceive we have many humans who are born with mental illness. Mental illness can lead people to act out in ways that can be harmful to others in the community.
What makes you assume that people will be born this way? Rockslider has shown that, biblically, there will be a significant change in the nature of creation. But let's assume that there will be mentally challenged people born, wouldn't a perfect, just God be able to address this issue? Is it necessary that we know how that is done? Wouldn't the event, should it occur, invite speculation of all kinds regarding this administration?
Is Jesus going to ensure that there is no mental illness? How will he ensure that human beings over-ride some of their more base behaviors and only "behave themselves?"
Such is the nature of the born again experience.
What about Jesus' administration will be different from the teachings of Christianity?
Because the joyous, over-riding teaching of Christianity is not about behavior, it's about relationship.
I ask because the teachings of Christianity have not made men behave themselves as of yet...and it has been a nearly 2000 year experiment. How will Jesus change reality or humanity?
It sure hasn't. What does this tell us? I'll say it again. Christianity is not about behavior - at least primarily, and specifically initially. Are you then conceding that man can not help but misbehave? I completely agree. Now you're left with addressing your legitimate concern about how The Kingdom of God has arrived.
Now, if peace means freedom from war
I can't agree with that. Peace doesn't just mean removing enmity in a religious sense, it means forming relationships.
then it looks like the Kingdom of Jesus is a fail since it will be established following the biggest war of extermination in the history of the earth.
See above.
War as a tool for peace is a contradiction and can never be so.
In a spiritual sense, I agree. However, war has often resulted in peace between governments.
War does not lead to peace. It never has and it never will.
It often has and will continue.