Please copy me on the answer, as I am not subscribed to the list.
To answer your question, here is one way:
(defun kill-matching-buffers-just-do-it ()
"Kill buffers whose names match REGEXP, without asking."
(interactive)
(cl-letf (((symbol-function 'kill-buffer-ask) #'kill-buffer))
(call-interactively #'kill-matching-buffers)))