Finally, my "Akschually" moment.
It's a FF IX reference, "To be forgotten is worse than death", but also because Alexandria wanted a happy going kingdom that knows no sadness or grief.
By wiping the memory of an individual, they made them forget the loss and they don't have to go through the well known steps of grief. But if you're forgotten, does it means you truly lived?
It's not "evil" it's just classic "the road to hell is paved with good intentions".