Where do atheists get the objective knowledge of good and evil to criticize God, if not from God?

Atheists like Richard Dawkins criticize God as "jealous and proud of it; a petty, unjust, unforgiving control-freak; a vindictive, bloodthirsty ethnic cleanser; a misogynistic, homophobic, racist, infanticidal, genocidal, filicidal, pestilential, megalomaniacal, sadomasochistic, capriciously malevolent bully." Where do they get the idea these characteristics are objectively evil except from God's revelation?