Guy put 0 thought into this.
Doesn't want him to go, cause they'll lose face.
But if he goes back to the guild and report to them that they got in his way causing him to not be able to fix the problem they also couldn't save, guess what? You'll still lose face.
It's more like "if we block him we lose face, but he also won't be able to get evidence of our crimes". So the lesser of two evils really.
At least that's my thought, since I feel like that Chimera is a creation and not a natural born monster.
Yeah all he has to do is;
"Oops, seems that his brainwashed and enraged dragons accidentally ate him in their blind fury, what a shame"
While I do get tired of the "I can't hurt the evil people" trope, in this once instance I will disagree with the plan to let the dragons kill the asshole.
The MC should know that if the dragons take the blame they're going to get punished, probably killed. After all in real life we do have to put down even beloved pets if they start attacking people, so there's no way a world that views dragons as tools isn't going to just start killing them if they turn on their owners.