A few things:
1. I see Touger translates the Rambam's "Davar" the same as you Goldin above. Now that I think of it, I stand corrected.
2. Might only apply to an actual Aku"m in the literal sense, not one who believes in shituf or one who attends a "social club" he calls a kloister, but is actually agnostic/atheist.
3. Both the SA you quoted, and the Rambam, qualify their din, which leads me to wonder if Damaxer's above statement is problematic.