This might be a case of, "We can't possible leave that family be, as the other nobles and the citizens would be be appalled by it, because of religious reasons." But yeah. Wasn't that smart. Now I understand why MC was SOOOO against being identified as hero. Maybe even because he knew, that emperor would take his family hostage. Well, no hostages anymore.
That guy is also a prime example of a person who believes he can buy anything with money, favors and blackmailing. He's such a dull character, I don't want to see him suffer that much. Just get rid of him fast.
So, when can we expect to see that emperor's head fly off?