Because discerning tone from ascii text is hard. How could you not have come across that fact before? There's even a law about it: http://en.wikipedia.org/wiki/Poe's_law

Also because is followup reference to "all the bikers there" is straight-up true, there are loads of bikers in London, really, though it doesn't follow from the statement before. Is that an attempt at sarcasm that fails because of a failed attempt at a false statement? Who knows. Why can't funkyy just say what they mean? Who knows.