What a load of utter bullshit.

Human's are not "fallen angels". Adam and Eve, where fallen "something", fallen "likenesses of God".

Every human born after Adam and Eve, and especially after Noah, are new creations, yet held to account for the sins of Adam and Eve.

The reason for God's cruelty is, God intends to beat humanity, as a blacksmith beats ore, to craft angel replacements.

How can something that knows neither of good or evil, resist temptation?

The only thing that exists is power. Those with power, wield it as a cudgel to force others to do as they will.