Atsushi was furious, a failed mission, pent up anger and YOU for whatever reason, you were carrying out orders like some sort of robot, so he snapped..

"But when an emotionless wind up doll like you starts being sympathetic, I'm doomed!" Atsushi says, glaring at akutagawa (you)

you murmured ‘im not a doll..’ which ticked him off even more.

"you are! You’d do anything you’re ordered to don’t you!? You'd kill yourself if dazai told you to, wouldn't you!?" atsushi yells out at akutagawa