It would of course depend on the reason. Completely wiping memories likely is far easier than replacing them. I know replacing memories with false ones isn't even possible in my world, but erasing them is.

[Because unlike most of Luceti, Leonhardt isn't fully convinced that the Malnosso as a whole do things just for their own amusement and a show of power. Some may, but it seems more likely that they have grown desperate enough that they care little about what harm is done as long as they eventually accomplish their goal of returning home.]