there has been statues of tengu, thats like saying in marvel comics that the avengers mustve had abe lincoln in it because you see pics/ statues of abe in the comic book. the reason there is statues is because that is a part of japanese culture.also you also see buhda's statue but you dont say that budha started the amakichi clan or anything.
it was never stated that it's chakra was darker. it is called sinister. sinister means "bad evil or wicked, threatening or portending to evil harm or trouble, ominous.
tengu: they arent evil in japanese culture either. they are protectors of mountains and forests.
uchiha madara: tell me where he is mentioned beside when the kyubi says he had more sinister chakra than itself, and where tobi says kono uchiha madara. even if he is the founder of the uchiha clan and is the statue its never stated yet. if the spoilers are true then he may be.
have you noticed that this theory is purely one of english speaking countries?
my friends who live in japan havent heard of it before. and they are narutards. they freaking dress up in cosplay for conv there
also put credit to where credit is due. this is yasha's theory on naruto fan. its called the dark history of the uchiha
to how the uchiha was created without tengu. the same way as the byakugan was created i would think. evolution or tampering with chakra. if the only way the sharingan could be developed was the tengu then how would you explain any of the kekkei genkai