"Imagine there's no heaven..."

MC Hendrick wrote a thoughtful post on what the world would be like if there were no God and everything were irrelevant. He makes the case that there is no freedom if there is no creator, since there would then be no objective set of morals, not ultimate purpose for our lives, and no reason not to do the sort of things we don't want done against us (murder, adultery, theft, etc...). I very much agreed with what he said.

Personally, John Lennon's "Imagine" never made much sense:

Imagine there's no Heaven
It's easy if you try
No hell below us
Above us only sky
Imagine all the people
Living for today

Imagine there's no countries
It isn't hard to do
Nothing to kill or die for
And no religion too
Imagine all the people
Living life in peace

You may say that I'm a dreamer
But I'm not the only one
I hope someday you'll join us
And the world will be as one

Imagine no possessions
I wonder if you can
No need for greed or hunger
A brotherhood of man
Imagine all the people
Sharing all the world

You may say that I'm a dreamer
But I'm not the only one
I hope someday you'll join us
And the world will live as one
(Source)

I understand the argument that many wars have been waged because of conflicting religions, but how would "living for today" bring about any peace? If there is no God, then there are no moral standards that might prevent starting a war for even more petty reasons. Furthermore, if there were no reason to abstain from certain activities in life that are harmful to others, why bother when I might gain something out of it?

To be fair, I am probably setting up a straw man here, but I think what I'm saying is ultimately true. If you are interested, Hendrick listed a link to another blog, No Religion Now, which basically argues the philosophy of John Lennon's song (WARNING--strong language). It is pretty enlightening from someone who has been a Christian his entire life (me).