Apparently you guys don't know about the law of Conservation of Ninjutsu. The less ninja on one side of a fight, the more powerful each individual ninja becomes. One ninja is one of the most dangerous things you will ever encounter. A portion of your brain knows this as instinct, which is why you think there are more ninja hiding somewhere- there aren't, but you want there to be, because one ninja all by himself is nigh undefeatable.
Also a ninja can beat a pirate because pirates are oft extremely drunk, and it's kind of hard to fight properly when you're completely smashed.
Pirates are cooler though.