I would've left the reveal at "You should be friends with him because he needs peers near his level to be socially adjusted so he can control his power." (read: a sociopath without them) For the girls the full reveal, with especially the part about familial execution, looked to be too much of a shock and that will underpin all interactions with the Hero and any friendship will be forced. Leaking that information won't be a problem if they don't know the full story, and those who can infer the whole story knows better than to tell everyone anyway. If they fail it's a moot point since with a berserk hero they might all be equally screwed.