SayUncle is wondering, "What’s the deal with the atheists who try to convert?...I understand why religious people try to convert atheists. They don’t want you to go to Hell and they want you to have eternal life instead of oblivion. But I see no motivation for converting a believer to non-belief."

There's a simple answer.  Some might not like it, so take it or leave it--that's your decision.

The answer is found in I Peter 5:8.  "Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour..." (KJV)

As tools of evil they seek to destroy those who are saved.  It really is that simple.