Everyone saying that MC should refute him, when actually this should be the quest giver job: he should state, as clearly as possible, that loose cannon will not be payed, even if he bring the daughter back on a silver platter. That's to prevent a huge liability to be involved in an extremely sensitive request.
What will actually happen is that quest giver will not complain about him smashing the table, spineless MC will take him in the party, he will cause all sort of problems, will try to steal reward money, spineless MC will forgive him and the author will even try to make us feel sorry for him.