The Essentially Good-vs.-Morally Responsible Argument for Atheism

In the spirit of Ted Drange’s 1998 article, “Incompatible-Properties Arguments: A Survey,” I wish to sketch the following argument for consideration.
Suppose we define “God” as a being who has, among other things, the following attributes:
(m) essentially good; and
(n) morally responsible for His actions.
Using these definitions, we can construct the following argument.

  1. If God exists, then He is essentially good.
  2. If God exists, then He is morally responsible for His actions.
  3. An essentially good being lacks moral freedom, i.e., an essentially good being cannot choose between good and evil.
  4. A morally responsible being has moral freedom.
  5. Therefore, it is impossible for an essentially good being to be morally responsible for its actions. [from 3 and 4]
  6. Therefore, God does not exist. [from 1, 2, and 5]

In order to avoid any misunderstandings, I claim the argument is valid, but I do not know if the argument is sound.
Cf. Wes Morriston, “What Is So Good about Moral Freedom?” The Philosophical Quarterly, 50 (July 2000): 344-58.