Neither are impossible positions to defend. Keaton doesn't have pouty lips (Adriana Lima has pouty lips), Keaton doesn't have a weak voice (certainly no weaker than Bale's), he's 5'10'' (cetainly not short, just not tall), and he was well before 40 at the time Batman was released. See, that wasn't so hard was it?
You seem to be basing your opinion on a bunch of comics and cartoons most of the people who will see any Batman movie, including me, have never paid much attention to. We don't care about fidelity to earlier incarnations of Batman, we just want a good movie. After Bale, Keaton starred in, from where I'm standing, easily the second best Batman movie. Most people seem to agree to that, if you believe the tens of thousands of voters on IMDB. I'm actually surprised there was any room for debate about who was the best, before Bale's turn.