There may be times when a Forum member becomes so annoying to others -- even without specifically violating any Forum rules/guidelines, that the appropriate remedy is just to deny service to them.
Replies, typically, only serve to perpetuate the behavior.
You may choose to ignore them or through the member control panel, have the software do it for you. Under the "User CP" link you'll see a "Miscellaneous" heading on the left side of the screen. Under it you'll see an "Ignore list" where you can add the names of such members.