Even though the MC is off balance, the elves didn't press him in a dirty way. And the MC was even got a very nice weapon. This guildmaster is the predatory one who sees that the MC is mentally off balance. So the guildmaster seeks to bind the MC with VERY unfair bargain requirements. The "belong to the guild" contractual requirement doesn't allow the MC to quit unless the guild is disbanded. It also feels like the kind of rights surrender statement legally be allowed in a society that allows slavery.