Could the message on the Georgia Guidestones be an Atheist Manifesto? Although the first guideline would be tricky to achieve I am sure our warlike nature and degradation of the environment could get the global population reduced sufficiently, given some time.

Maintain humanity under 500,000,000 in perpetual balance with nature.
Guide reproduction wisely improving fitness and diversity.
Unite humanity with a living new language.
Rule passion, faith, tradition, and all things with tempered reason.
Protect people and nations with fair laws and just courts.
Let all nations rule internally resolving external disputes in a world court.
Avoid petty laws and useless officials.
Balance personal rights with social duties.
Prize truth, beauty and love - seeking harmony with the infinite.
Be not a cancer on the earth - Leave room for nature - Leave room for nature.