It's quite revealing that Pope Benedict XVI wasn't willing to discuss the matter at all. Religious belief is not very rational even when it's being inoffensive but refusing to talk about an issue this huge is intellectual cowardice.
I'm often told that I've misunderstood what the Catholic church teaches, but from what I can tell the Pope is this god's representative on Earth. You'd need to have contact with someone to represent them effectively, so it's not unreasonable to assume that god should be giving answers to his spokesman about an issue which bothers him so much.
So, with all that being the case why won't the Pope enter any discussion about it? I'd expect something like this from someone so sure of their convictions:
Opponent: "So why shouldn't we have female clergy given that they're equally capable of defending their faith?"
Benedict: "I know it seems unfair, but it's because [insert perfectly rational and sensible reason which nobody could object to here]."
Opponent: "Oh, I see. Fair enough then."
From this we can draw one of two conclusions:
1. The Pope and the Vatican aren't confident that they could defend their convictions.
2. The Pope isn't actually getting much advice from this god and he's continuing with his own prejudices.
Either way it doesn't give them much credibility. I might not believe in any of the church's teachings or mythology but women should have equal opportunity to participate if they want to. Sexism isn't a good look for anyone, male or female.