^This.
Most of the Shichibukai are modeled after real life privateers. Most of which were religious.
"Bartholomew Kuma has a bible (notable as it has "BIBLE" in full capitals) in his hands and always carries it with him. Gekko Moriah wears a cross around his neck, Mihawk also has weapons modeled after crucifixes, so one could say the Shichibukai might be a holy organization. However, the religious emblems they carry could simply be due to the fact that the privateers they are modeled after happened to be religious. On a separate note, while the country of Alabasta looks to be a Middle Eastern land, their graves are cross-shaped. The graves in Fishman Island's Sea Forest are also shaped like crosses."
