The Darwin fish does predate the rancorous Creationist debate. I remember them from college (1968). I never took them as especially mean-spirited, any more than the old chant, "I don' care if it rains or freezes, long as I got my plastic Jesus." Irreverent, but not intended insult anyone. Of course, these days the distinction between "insulting" and "irreverent" has been lost.