Seth Andrews mentioned this statement in his most recent podcast of The Thinking Atheist: https://www.youtube.com/watch?v=3wezX8XXWnM. It is said in many different ways, but it is something a lot of atheists have heard. It is meant to shut down a conversation. It is meant to bully us into silence.
So who are we to question God? We are humans just like every theist. We have the same access to knowledge that theists do. We have the same basic abilities that theists do. And we have the same rights that theists do. If a theist can proclaim God’s (or a god’s) existence, then we can use our own knowledge and understanding to proclaim the opposite. If theists can say what God wants or doesn’t want from us, then atheists can question that claim.
Who are we to question God? Well, for one, we aren’t questioning God. We don’t believe in God. We are questioning you. We are questioning your claim that God exists. We are questioning your claim that God wants what you say he wants. For another, we have every right to question you, just as you have every right to say what you believe.
Who am I? I am your equal. You don’t get to shut me down because I disagree with you. You don’t get to bully me. You don’t get to take my voice away.
As for God, he can speak for himself. If he wants me to do something, he can tell me himself. And, if he were to do so, then I would question God.