It's both funny (and sad) because it's completely true. Dang, I've never been more embarrassed about crybaby fan-boys until now! This direct over-reaction has happened at the announcement of every Actor who has ever played the character.
Back in 1989 a small group of people got together and sent Warner Bros a petition over the choice of Michael Keaton. Just recently, when it was announced that Heath Ledger was going to be the Joker in The Dark Knight movie, some people totally flipped-out! (He won an Oscar). I say hey, give Ben Affleck a chance. Wait until you see his performance and THEN make a judgement.