...so what we're saying is, that with shuriken, a highly trained martial artist can take out someone unarmed, unarmoured, incapable of dodging, and without a good pain tolerance. You do realise the same applies to pencils, small rocks, and bare hands?
So your evidence: A: there are plenty of ancient shuriken around in exhibitions and so forth, dating back to the heyday of ninjas, You know what else existed at the same time as ninja in Japan? Cranes. I thus theorize they used them as weapons. B: there are any number of sites that tell you how to THROW shuriken, arguing the fact that they were used in that fashion for some time, There are websites that tell you how to make sushi, arguing that sushi was made in this fashion for some time. I thus theorize sashimi is a weapon of ninja. C: there is the aforementioned art of 'Shurikenjutso', which, I believe, is specifically a ninjitsu art, although I could be wrong er... yes, I think the evidence proves you are certainly capable of it. Unless you have evidence shurikenjutso is a ninjutsu art. D: nothing I've read anywhere else on the internet says anything that I can recall about the shuriken NOT being one of the traidtional ninja weapons, I've never seen anything saying ninja didn't clog dance. Irrefutable proof this was their main method of killing. E: if they didn't use them, who did, may I ask? Name me another group that used them - I certainly can't think of any. We don't know who used the Antikythera Mechanism, but I don't think it was ninja.