Been otherwise engaged today, alima. I wasn't ignoring your question from this morning. I do see that (the fact that) the phrase don't piss off the fairies jars with some people, but I think there's a huge (HUGE) difference of connotation between a piss and a fuck. Fucked off could be interpreted to mean raped to someone who hadn't heard the expression before, depending on the context. So the context is still the most important indicator of meaning and, therefore, whether one need feel upset/jarred/offended or worried on someone else's account.
There will always be different interpretations of meaning for any given argument or joke, story, or, forgive me, innocent piss-take.