John Lennon's Imagine from Imagine. Imagine everything is meaningless, and people only live for the moment. Plus, nothing to kill or die for? That means there's no freedom and no love. And this is supposed to be a Hope For A Better World song.
The Fridge Logic of that song is that what he's describing is his own personal BoringHeaven, while mentioning the idea of heaven as one of the evil influences on life. Of course, he's talking about people striving towards a heaven after life, as opposed to trying to create heaven-as-a-place-on-earth (oooh, baby, do ya know what that's worth? sorry...)
It seems significant that the original person who posted this apparently thinks that freedom and love can't possibly exist without people killing each other or dying for them. When the song itself implores the listener to imagine a world where there could be love and freedom without death and destruction. Perhaps such a concept is beyond the boundaries of their imagination.
I think the OP was pointing out that most good things, such as freedom and love, are things people see as worth killing or dying for, not that they can only exist if you kill or die for them. A lot of romance stories revolve around the idea that love is worth dying for, after all.
But the whole point of dying for something is that you eliminate a threat to it. If there are no threats to love or freedom, how can you kill or die for them? You already have them, and they're not going to be taken away.
It is also worth simply noting that "Imagine" is a three-minute pop song, not a detailed political manifesto. Lennon's simply asking his audience to, as the title suggests, imagine a world with or without the things he raises, but what such a world would look like would vary according to the listener's imagination. Lennon presumably had his own ideas, but he's under no obligation to provide the listener with a carefully researched and costed step-by-step plan for achieving it; all he's saying is that if you want such a world, then imagining what it looks like is the first step towards eventually actualising it.
And many people have pointed out that "imagine no possessions" conflicts with Lennon and Ono's massive wealth. When Neil Youngsang "Imagine" for the Firemen's Fund tv special after the September 11, 2001 attacks, he changed "I wonder if you can" to "I wonder if I can", highlighting the hypocrisy of an artist worth over $65M singing such a line.