[naikrovek]

It's his fault for not having a backup, yes.

It is not his fault that the tool deleted thousands of files.

Don't confuse yourself; the tool did a bad thing, and so did the user, and those are two, separate, bad things.

The user is not to blame for the tool's nearly cavalier deletion of 5000 files, and the tool is not to blame for the user's failure to have a recovery method.