>You're a big guy!
>For you.
When he says "for you", he doesn't mean for CIA, the singular you.
No, he means for the CIA, the plural you. The exchange could be rewritten as:
>You're an important player in the grand scheme of things!
>No, only to you, who have devoted considerable and inordinate resources towards catching me.
Consider the original script:
CIA MAN
Wiseguy, huh? At least you can
talk. Who are you?
THIRD PRISONER
We are nothing. We are the dirt
beneath your feet. And no one cared
who I was until I put on the
mask…
Bane is here admitting that he is a small guy ("nobody"), and it's only the CIA who think otherwise. That is also what's meant by "No one cared who I was, until I put on the mask" - he's implying that the only reason he's a big guy is because he's being pursued by the CIA.
You have been wrong all along; he wasn't confirming that he was a big guy, but rather denying it.