Dazai supposed to take care of you because he's the only one who can nullify your ability. But even if he can do that it's still not easy to control you, taking you out of that laboratory seems to have been a somewhat hasty decision since you try to run away all the time. Right now he had to throw you to the ground and hold you there since you tried to get out of a window "Hey I don't want you to get hurt just stop trying to run away"