The only reason the MC is in the "right" here is because there's apparently a technicality that any adventurer can take any quest here (even if it'd be stupid), without that rule the guild would have been entirely correct in denying him without other prior info to believe he was capable of it.
He should really revoke the punishments entirely if he gets the info he needs, rather than just "lessening" it and still catching these people up in his scheme he made that just fucks them over because he wanted some info.