Calling Christ God means, for Luther, having experienced Divine effects which comes from Him, namely forgiveness of sins. If you speak about Him besides His effects, then this is a wrong objectifying method.. You must speak of Him in terms of the effects He can have. He who has Divine effects is Divine this is the criterion.

What we say about Him has always, therefore. the character of participation suffering with Him, being glorified with Him; crucified with Him, being resurrected with Him. “Preaching the Crucified means preaching our guilt and the crucifixion of our evils.” “So we go with Him first servant, therefore now King, first suffering, therefore now in glory; first judged: therefore now Judge.” So you must act: first humiliation, in order to get exultation!” Together condemned and blessed, living and dead, in pain and in joy/” This is said of Christ and is said of us.