What if I accidentally create a god that destroys mankind?

Just look at the hubris behind such a statement. It presumes that a mortal man is EVEN CAPABLE of creating a powerful being with reason and free will, which furthermore will be super powerful and capable of monumental feats, both bad and good.

If a man said this, you would dismiss him as crazy. But unfortunately, many men are crazy today.

Just replace "god" with "self-aware Artificial Intelligence" and you have literally millions of men who believe -- on faith -- that such is possible. That is, the false religion "faith" of science of course. There is talk of needing to put limits on AI, the Singularity, etc. We need a term for this exaggerated, religious faith in Science: sciencism? scientology? (that's already taken) science worshipers?

In a related vein, some men fret about how mankind is going to destroy the earth by irrevocably altering its climate. Poor man, you must realize that you are insignificant and have no effect on the earth's climate. The earth can release more CO2 in a few weeks by literally passing gas (better known as a volcanic eruption) than all the industrialized countries in the world can produce in a decade!

Is there no limit to the folly that hubris leads to?

It is a philosophical, metaphysical reality that a creature can't create something on a higher order of being than itself. A rock can't create a plant. A plant can't create an animal. An animal can't produce an immortal soul. An electronic person or creature in a video game can't create anything "in the real world". 

Anyone who believes that man can create a godlike being believes that mankind is already a god!