@dlowan,
If God is defined or described as that which is (omnibenevolent, omnipotent, omniscient, etc.) then that God is omnibenevolent ...does not follow.
imo, This fallacy is the error of the ontological argument.
God = (the x such that: x exists and x is (omnibenevolent, omnipotent, omniscient, etc.)), implies,
(the x such that: x exists and x is (omnibenevolent, omnipotent, omniscient, etc.)) exists ....is not true.
Rather, this description of God, exists, if and only if, it is unique.
F(the x such that Fx and Gx etc.) if and only if (the x such that Fx and Gx etc.) is unique, is a theorem of predicate logic.
If there is any truth directly about a God then that God exists.
If you can confirm that your God, however it is defined or described, has any particular property then that described God exists.
Lots of Luck, with that one.