Fen is a derogatory word and the Martha fans invented the word "batshit" just to oppress us!
Doctor Who shipwank ahoy! jesidres makes a post about Rose fen being molested by those horrible Martha fen who invented the word "batshit" to be mean to Rose fen, or something. Except, oops, "fen" is a derogatory term. And so is calling someone blond(e).

My personal favorite part is when leighleighla admits she hasn't found any of these posts with the Martha fen attacking the Rose fen, and concludes that this must be because the Martha fen are like ninjas!

Bonus: wank_report mini-wank where this was reported!