These guys are (fill in your own perjorative clause). They deserve to have the snot beaten out of them, or at least to face jail if you're a more civilized sort.

But, having said that, don't you have backups? Because, speaking practically, this is no different than experiencing a hard drive crash - recovery of your data would be terribly expensive, if it were possible at all. If you've got backups, though, recovery just takes a little bit of your time - these extortionists would have no hold over you.