If the Divine Command Theory (DCT) proponent is to defend his position he must demonstrate the necessary falsehood of the counterfactual: If God did command rape then there would be a moral obligation to rape. There will be an assumption of ethical realism since ethical anti-realism is argued for and against in completely different arguments. The ethical realist objector [to DCT] claims that it is possible for God to command rape in some possible world, or in an impossible world close to the actual world, making it obligatory for all moral agents, whereas rape is still morally bad in that same world, thus, making DCT arbitrary and is defeated.
Here are the symbolic references:
(RIGHT) ∀ϕ☐(Rϕ ≣ Cgϕ)
(WRONG) ∀ϕ☐(Wϕ ≣ Cg~ϕ)
(CONTCOM) ∀ϕ[(◊~Cgϕ) ∙ (◊Cgϕ)]