You don't know much about ninjas, do you? Ninjas were espionage experts, had an art for their purpose called Ninjutsu which involved skills in many areas including armed and unarmed combat, so they were plenty good at fighting. They were basically assassins/thieves/spies/other stealth based occupation from Japan. There's no reason to say they were less skilled than someone with a similar occupation from another country.
http://en.wikipedia.org/wiki/Ninjutsu There's some info for you on what ninjas actual skills were. I think what you were thinking of is random South American tribal hunters. Who are unusually bad at fighting.
I think he meant Ninja, but he got a few things messed up on it.
Ninja's did use blow darts and they did modify tools into weapons. Ninja's were bad at straight up fighting, they had a low chance of winning in a straight up fight, they were assassins and spies, they weren't dedicated samurai warriors and they wouldn't be able to fight as well as one with a Katana, Ninja did have many ways they could kill and they'd probably still know how to use a Katana better then the average person on the street, but Samurai trained hard at their style while Ninja were more versatile and stealth based. Samurai use to be good at archery at one point too, but like Europeans, it seems there was a whole honor code and as such made archery a bit less important then the sword play, so the average samurai may have been inferior to a ninja in archery...