it is possible to say fuck off to someone to their face, in such a tone that it is not offensive

I think that is very true, particularly in Ireland and Scotland where common usage of the term has rendered it almost jocular! I am reminded of the Australian cricket captain who, on receiving a complaint from the England team that someone had called them bastards, gave the classic line "Which of you bastards called these bastards bastards?" Could be an urban myth but I hope not :-)

We have had plenty of discussions on here about so called abuse and insulting language. I believe that bad language is often the least of our worries when discussing more serious matters.

Cheers

DtG