I think part of it is that Posey is so "valuable" that they want to
protect their investment, so every ding he gets is magnified. If
Cabrera, a much bigger guy, was moved to 1B, then it makes sense to
move the more fragile Posey too. But putting him at 1B makes him
much less valuable.
I like the idea of trying Posey at 2B though, even though I think
he's too slow to play middle infield. College is different. He was
probably the best fielder in his school so he played SS. If he can
play 2B at the pro level, they probably wouldn't have put him at
catcher. And at the rate Uggla is making errors, how much worse can
Posey be?
But now that Hector is out, Posey has to play catcher, unless the
backup catcher can hit.
BTW, I don't know if Posey takes a beating more often than other
catchers or not, but I'd say Hector does. It's unreal how often he
gets nailed. Some are his fault, bad technique or bad hands. But
some are just bad luck, like the 2 foul tips that knocked him out of
the game. Nothing you can do about those.