Should they live in the shame and horror of this person that they probably attempted to curb at some point.
No. Those relatives that have not enabled or supported a monsters actions are of course completely innocent.
And if they want, they can of course mourn the loss of the ability to ever have a nice conversation with that person again.
But a burial is not like mourning in your bed, crying yourself to sleep. There you can accept that you are sad about the loss, even tough the world is a better place without that person.
A bureal however is a public performance that, as you say, is for the living. Not for the dead. It is not useful for mourning, but a ritual to pay the last respects to the deceased person. Not only for their good side, but also for their evil side. And the bigger the burial, the greater the (implied) respect. This holds true in any western/materialistic society, and was practiced in ancient times, where pyramids were built to honor kings, and a bigger pyramid implied a better king.
Therefore holding a large burial for a horrific person signals to the living that you not only miss that person as a friend, but also support their actions and choices in life.
I am running BTRFS on multiple PCs and Laptops since about 8-10 years ago, and i had 2 incidents:
I am using BTRFS RAID0 since about 6 years. Even there, i had 0 issues. In all those years BTRFS snapshoting has saved me countless hours when i accidentially misconfigured a program or did a accidential rm -r ~/xyz.
For me the real risk in BTRFS comes from snapper, which takes snapshots even when the disk is almost full. This has resulted in multiple systems not booting because there was no space left. That’s why i prefer Timeshift for anything but my main PC.