It's a bit surprising that the "he blew up a monster protection facility" thing is so questioned. Like, obviously the kingdom's more at peace with monsters now (from how they treat the girls), but iirc washio was only summoned 10 years ago, meaning that the time between the kingdom being at war with them and the war ending hasn't been that long. You'd think they would maybe at least question when he did it, whether it was current kingdom policy or not.
Though I guess it's possible that the whole "hero kills monsters" thing was a secret from the public. Either way, I'm hoping that with Rimnoa's reaction here, he'll at least stop being such a bad guy when he (hopefully) learns the truth, and maybe just transition to being a legitimate rival character.