It means everyone should get a long and not harm each other for any reason.
Yeah, there are some radical leaders. But in this time period, the United States has been the cause of most of the violence we see today.
For example, the terrorists. They are only terrorists because we install dictators in their country, kill innocent people, and send weapons. We are our own enemy. Every innocent person we kill over seas, more people end up joining the terrorists.
Our foreign policy makes no sense at all, we bomb Pakistan and at the same time provide them with foreign aid. We are invading countries that haven't done any harm to us directly.
We should be trading with countries and try and avoid war as much as possible. We spend trillions of dollars just to sustain our presence in countries the American people can't even point to on a map.
We couldn't get rid of all the violence in the world, but we could make it a lot better if we just removed our military from 130 countries. That is right, US military happens to be stationed in 130 countries. What if Chinese troops were stationed in the US. We probably wouldn't feel that comfortable.
I think we need to wake up and deal with this problem. Nothing will change, until it is too late.
To close, yes, I wish we had peace on earth. I think peace on earth means doing the opposite of what I stated above. At least it would be a start to reaching that goal.