Bulk User Shred

I have a file populated with users created by way of spam. I’d like to remove
them all in the most efficient way possible. Right now the only method I can
think of is to use the UI and manually select each user then run Shredder. What
I would prefer is to have a cron job that runs Shredder via the CLI much like I
do with tickets that have been deleted.

Has anyone automated the removal of users this way? Is there a built in way to
use a file as the source of usernames to be removed all at once?