Have a look at this. It's the concluding part of a debate hosted by the BBC in July (you can catch the other 4 parts on you tube and they're well worth watching if you have 40 minutes to spare). In this one, the audience votes after hearing the arguments for and against the motion "The catholic church is a force for good in the world." The results are astounding -- but then the two arguing against the motion were Chris Hitchens and Stephen Fry. A formidable pair.
I doubt that any of the swing voters were catholics, but it's still heartening to know that a well-expressed argument can change people's minds,