Reverse pruning - delete from a date?

[Outlaw Mantis]

Everywhere I've looked I seen that there "isn't an option" to delete users and to just use the prune feature. I've had a spam army register on my forum when I forgot to close it with registration protection enabled. My fault I know, but I have to fix this! However, the prune option is only for past dates.

The forum has been closed for a long time now and I plan to reopen it. This means that the mass registration all happened from a date when no human registrations were made. Therefore, an option to delete users from a date would fix the problem entirely. I can't delete users individually because there are so many, I'd be a skeleton. :erm: I thought about running an SQL query but fortunately read that it could wreck the forum before I actually did it.