I don't think I've ever preached anything apart from non-violence in my activist days. I certainly never preached atheism. Preaching is a particular type of speech, not just any old speech but a specific type trying to win over converts. Even when writing to agnostics on this forum, I limit myself to asking if they are atheists as far as the easter bunny and the tooth fairy. That's a straight forward question, not preaching. So I think this song has it wrong.

As an atheist I don't sell a lot of opinion, I just question yours.

All you need a backing track:

Funny what people will debate....

I perceived that there is nothing better for them than to be joyful and to do good as long as they live; 
also that everyone should eat and drink and take pleasure in all his toil—this is God's gift to man.  - Ecclesiastes 3:12, 13.

If the dead are not raised, “Let us eat and drink, for tomorrow we die.” - 1 Corinthians 15: 32b.

Take your pick!

John Lennons 'Imagine', kind of hits those points.

Give it time....if not, it'll be such a waste....has the basics of a country tune.

I certainly don't know, others have Googled that, I prefer we are stardust, we are golden.

I've never preached atheism and I don't know anyone who did.

No atheist ever knocked on my door to try to convert me. I don't preach to anyone. If people cannot use logic and intelligence to figure things out themselves, then people can stay in their delusional fairytale life and beliefs.

A Google search on the first two lines did not bring up any song lyrics. This doesn't mean you didn't hear it in a song, but not one popular enough to have been written out where Google can find it.

It sounds familiar but I cannot place it

Possibly...but if not already it should be!

I wouldn't care one way or another, although non believers do not preach at all.

Atheists don't preach. Or come to your door to impose their beliefs on you. These are important distinctions.

I HOPE you just made it up.

Probably a song somewhere.