If I recall correctly, it was Alexander Dumas who told a story in his histories of a Hun who visited Paris, learned of the excesses of the Borgias and announced his intention to visit Rome to see for himself. He visited Rome, converted to Christianity, and came back. His hosts were surprised and asked him why. He explained that he witnessed the corruption of the priesthood and cardinals, the goodness of the people and the extent of their devotion, and determined that if Christianity could produce these results even with the corrupt priesthood it must of necessity be True. So he converted.