"They seem to care about their data somewhat, which of course means they have off-site backups."
I don't think a reply of "there are classes of data that one can care about and still not have backups of" is unreasonable.
"...I can surmise is that they're confused"
Again, I think showing a few cases in which users can have perfectly non-confused reasons for using these filesystems is pretty straightforward as conversational gambits go.
The article wasn't about using RAID, it was complaining of a lack of RAID60 and triple parity in btrfs, and a lack of volume expansion features in zfs.
Well, yes but I don't think either of those things are really addressed by "care about data IFF backups exist". I guess I either don't get what point you're making or we're just getting distracted by phrasing.
I don't think a reply of "there are classes of data that one can care about and still not have backups of" is unreasonable.
"...I can surmise is that they're confused"
Again, I think showing a few cases in which users can have perfectly non-confused reasons for using these filesystems is pretty straightforward as conversational gambits go.