He should take the team on a bandit extermination mission and let only the genins do the job, this way they would have to either kill or be killed and if they refuse to do it then give them a very very severe punishment and then again take them to do a job where they will have to kill.
I don't care about your disturbed vision, haku is a man and always will be, And you're wasting a lot of time getting the MC to train kids, speed up a little bit please.