As I said, it was an in joke.  I and my friends often say "fuck off" and "fuck you" to each other. The origins are irrelevant. 
I'm still amazed how upset people get with a word though. I still can't see how it disrupts anything nor how it is in opposition to any policy. If I had "f*ck you", it would mean the same thing, but I doubt anyone would get upset.  ~AFA.