"Why do we seem to have this ridiculous need to believe in a moral accountant?"

Frustration that reality doesn't reflect our ideals and how we think the world ought to be.

"All is for the best, in this the best of all possible worlds."

Voltaire may have meant it as satire, but how is the delusion in his masterpiece any less absurd than this OP's claim objective morality exists?

Yet he...

• Can't evidence it.
• Can't accurately define it.
• Can't offer a single example of it.
• Can't explain where it is derived.
• "Feels in his heart" it's real.
• Can't cogently explain why it's better than secular morality even.

I mean come on, what's to debate here? He's comparing reality to naught but his sentimental wishful thinking of how he wants everyone / everything to be.

Asking why aren't evolved apes always kind to each other is not a profound examination of reality. It's a profoundly stupid delusion to expect an evolved primate to be perfectly moral in the first place. Morality is not an end goal, it's a critical examination of our actions and behaviour, and that evolves continuously. Making up fantasies because you find reality dissatisfying no more improves morality than it changes reality.