I disagree with that sentiment.
I'm sure it would have been easy to sit back in 1700 and say "you can't be serious, we will never reach the Moon, that's an absurd idea..".
I think the idea of something seeming impossible contributes to it's demise. What ever happened to 'nothing is impossible'? What gets me is even if it was impossible, shouldn't we still try? It's like saying "this fire in the pan is too hot!" then walking away and letting it engulf your whole house because you thought it was impossible to put out. Saving your house, like ending war, is worth the effort, however impossible it might seem. That realization, coupled with removing the profits war creates for certain industries and a steady decline in organized religion (along with a dozen other things) are, imo, probably what will lead to the abolition of war, and I think it'll take at least a century or two from today for any of that to actually make a difference, but I think we're on the right track.
What I think would be interesting is getting some kind of international petition going, something completely apart from the governments that rule the world. Strictly civilian. When you take away all the barriers and borders, most of us want the same things. We want to live peacefully and raise a family without fear, violence or intimidation, live our own lives as determined by ourselves in ever aspect of life, just live happy and be free. Governments are the organizations that put up barriers, make our neighbors enemies one decade and friends the next. They're the ones who benefit from ongoing conflicts. The ones that scare us into submission.
An international peace treaty, with hundreds of millions or even billions of signatures couldn't possibly be ignored. If you could organize something and get that many people to declare war is an inhumane practice of the human condition, it couldn't be ignored. Something would have to happen.
Get all the nations of the worlds civilians to cooperate with this simple treaty, with the internet, the possibilities are endless...