It's funny that you say this, because I was going to say something somewhat similar at first, but I was caught between saying our actions wouldn't do much because it's really up to the people in power, and saying what I said; concurring with your view. I resolved though, that the former argument does not hold water. Not as much as it should if it's going to be a public or voiced-out opinion.
Basically though, it just means that, while our never going to war again and maintaining peace may be largely up to our leaders' decision making processes, we also can put in the effort in our own small niches to prevent it. It's like you said, we should do our part and hope it'll be enough. Greed, selfishness, etc., these are abstracts, how do we fight them? Can we? Would we win?
If we all loved one another, maybe there'll be no conflict for the rulers to capitalise on, right? Argh! As I type, rebuttals come flooding into my head. This is a sit-down-and-really-talk-about-it-kind-of-conversation. I should let you go.
Peace!
Loving one another, oneness, and seeing the world as one country with all mankind its citizens...sounds ideal right? But here's the thing, we can't agree on that scale. We don't like each other for many reasons, religion, politics, colour, social standing, country, intelligence-level, how we look, talk and other factors. Humans are judgemental and prejudiced...so how are we going to love each other? Can't.
Sad I think, but humans have it deeply ingrained that greed is good, that we need more than we actually need and that taking it from others is how to proceed. Of course, those others will protect what they have and...war.