Note how AP declines to capitalize "Pope" in the headline.
I think if you just right pope by itself, not followed by a name, you don't capitalize. Example: "The pope is travelling all week."
Whereas, you would capitalize it if it had his name after pope. Example: Muslims would love to slip Pope Benedict's throat."
Another example would be "The responding unit was Officer Johnson." and "The officer responded to the 911 call."
I reserve the right to be wrong.
I didn't capitalize "pope" because I'm not a Roman Catholic.
TheErnFormerlyKnownAsBig is completely right. Words like "pope," "king," and "president" are not capitalized unless they are used as titles, according to both the widely used Chicago Manual of Style and the AP style manual. This is a grammatical style choice for consistency. Please don't try to make it political or religious, because that's ridiculous!