@MooseNucle
Agreed but the Emperor is just as stupid.
"Oh hey, I guess his whole family exists right next door - we could use them as hostages or maybe-"
"DECAPITATE"
Yeah that's a plan. Start a fight with someone you're just assuming to be a Demon Lord. Again, they have no idea if he actually is or isn't, they're just assuming he is because of what he can do. They have a claim that he was a Monster Tamer, yet chose to ignore it and call him a Demon Lord. But why? It's nonsensical. If they hadn't heard of the Taming class then why not say so? Because they immediately just say that he MUST be a Demon Lord. Even worse, they know how strong he is by how easily he defeated an S-Rank and they immediately want to start a fight with him. AND EVEN WORSE - what has he even done to warrant such actions taken against him? He should just be classified as an aberration and kept a close eye on.
If the family is still alive then they could be used as a bargaining chip, you can also argue to forge an alliance, even if temporary while you assess the person in question.
If the Emperor doesn't have some bigger grand scheme I'm pretty disappointed by his actions. Everything going on is just stupid by everyone. Literal pea brains.