John was a little naive.
Don't get me wrong, I love The Beatles and especially John. He was always my favorite. But when real questions about the state of the world were asked, his only response was always just to give peace a chance. Now that is always something to strive for as individuals, despite the fact we will always fall short of perfection. But our nations representatives can't go into Cuba, Iran or any terrorist cell and simply say "hey guys, let's just give peace a chance. OK." shake hands and sing we are the world. There is evil in this world we live in that will NEVER EVER give peace a chance! To me its a nice message, but too simple for the complex world we live in. Its more for your personnal life. My local priest said "we can't make the world care. WE just have to care."
What I like about John, as compared to todays "peace" celebrities, is his message wasn't about tearing down any specific country. He believed there was a certian hypocracy, or ambivalence, even within the peace movement itself. His was more of putting forth a positive message rather than always criticising. When he did criticise, which he certianly did, he spread it around. He didn't believe any nation to be more "peaceful" than the other. Also, he wasn't shy about criticising himself. IMO.