Man this really drives home the twisted nature of the Pointed Hats' rules. Memory Erasure may seem humane (especially when compared to death or medieval punishments), but it removes something that makes you you. In this case, the Pointed Hat lost all of his life experiences, his loves, his passions, his fears, his regrets, everything. Giving this one Magic Control organization ownership over all of that for every person ---- it's a bit despotic. Even in small doses, that's a lot power for people this trigger-happy.
And Coco + Tartar are stuck in a hell created by the Pointed Hats' rules. Because they know that their leaders won't help the people they care about (i.e. Coustas), these 2 kids are trying to solve problems way beyond their paygrade. Showing the High King a man with a magical glyph tattooed on him sounds like a horrible idea. Coco and Tartar have no way of controlling the fallout of what the king does next. But it makes complete sense why they'd turn to that route. They're in way over their heads and they need someone with more experience to help them.