Are all atheists this ill-informed about religion?

[Mudhammam]

State the differences.

Sure. From dictionary.com:

benevolent: characterized by or expressing goodwill or kindly feelings

good: morally excellent; virtuous; righteous; pious

While I didn't define these, I illustrated them earlier with an example, which everyone has ignored. Expanded version:

A judge is sentencing a convicted murderer. The judge tells the man that he's really good at heart and sentences him to eat a piece of chocolate cake, then go on his way. This would be benevolent of the judge, as it expresses goodwill and kindly feelings. It would not be good of the judge, as it is not morally excellent or righteous.

Regarding god, judgments such as the flood are obviously not benevolent, but they are from god's POV righteous, and therefore good.

What difference does all of this hairsplitting make with respect to the evidential problem of evil? Your larger error is that you concede that God's malevolence is accurately characterized in the biblical flood myth yet insist that this doesn't imply that he isn't all good.