I think it's pretty friggin obvious. Pirates have absolutely no power on the land. Even on their ships they have parrots who say stupid things and then lasers....that's it folks. Vikings.....puuhleeeze, the walk around with long hair and just rape and pillage women. And they wear stupid helmets and can't even player guitar, they play the wussiest instruments of them all, flutes and lires.
NINJAS on the other hand fly around non-stop. They've been known to pop over a million boners, pork a thousand babes in a day, and WAIL on guitar...HARD!!! They also can eat copius amounts of spicy chili in their dojos. If even a thousand or a hundred pirates and/or vikings attacked a ninja they'd be in for a huge surprise....how about a huge hippo six foot boner uppercut?!?!?!?!?!?!?!?!?!?!?!?