The Sengoku period was a time of civil unrest between 1467 to 1615. Shinobi or ninja capitalized on this as covert mercenary agent in the feudal system, though it could predate as early as the 12th century. Their covert espionage, deception and stealth attacks were deemed dishonorable and beneath the honor of the samurai, who despised them with great prejudice. Though some traditions and fighting styles or techniques have undoubtedly been shared through the generations, a contemporary white American just has not lived the important cultural experience of a Sengoku period agent of disorder and assassination. They just haven't. They have not felt the prejudice of the samurai or the brutal warlords who would exterminate them, nor have they lived during a time where such drastic methods were necessary. No, Los Angeles in the 80s does not count. It is even more insulting considering that as the Edo period dawned, need of their skills and spycraft ebbed, and they were no longer able to provide for their ninja families, and were forced to seek other work. The very excess and abundance of the modern world that would allow a white American teen to treat ninjitsu as a frivolous hobby, or Weekend wakizashi, was not available to the downtrodden ninja.