Yet the intent may have just been to be blunt, or there was no intent, just exasperation/annoyance.
It isn't a question of 'allowing' anything.
Personally I think that everyone who has a problem with a particular person or post should ignore it; that would end the problem. I'm all for debating opinion, even arguing stuff past the point where anyone is going to change their mind, but personal attacks, perceived or actual, should be ignored. Forum moderation is best restricted to dealing with spam and moving the occasional misplaced topic.