Even in a normal state, anger can cloud one's judgement. Anger can make a person temporarily insane and do what they normally wouldn't do.
But this is just the effect of anger as an internal enemy. One can imagine how bad things can get if he liberates in anger.
He can imagine it easily. And from what he can imagine, it will not be a good thing to deal with the corruption of his soul by his divine flesh while blinded by his anger.
Besides, even if he liberates his divine form, wins the fight, and somehow manages to regain control. He will still have the angel of killing to contend with.
So he didn't dare liberate his divine form. He could only swallow his anger. This became increasingly difficult as he watched the people of his city, which are his properties, be killed like chickens.
He became tempted to take action against Legion. But first, he decided to use spirit sense technique to test Legion's power.
