Why not? Christian Bale sucked as Batman, his acting in the Batman outfit was as bland and senseless as Clooney's and Kilmer's only Bale decided to throw in a voice like he had severe laryngitis. And don't get me started on Frank Miller. Trust me, considering the route the DC Universe is taking, Affleck is actually a great choice. He can breath life into a character that has been plagued by efforts to try and make a dark and gritty storyline about someone who runs around in his underwear fighting criminals because of unresolved mommy issues.
Oh sorry if i don't like Batman as a psychotic pedophile and think Frank Miller is a piece of shit for his ignorant political views and overt misogyny in his depiction of female characters. Relax though, even if Affleck COULD save Batman, he probably won't be able to do it under the strain of the new stupid Man of Steel depiction of Superman. Besides, i thought you'd be less outraged at Affleck as Batman and more outraged at Justin Bieber as Robin.
You are entitled to your opinion and I respect your views as well. While Justin Bieber would not be the choice I would have for Robin, the hypothetical is null in void since it has not occurred. I thank you for your time and have a pleasant day.