Re: Dobson and Arikawa Sensei
I'm not sure what you mean by marginalization. Peter is certainly correct - and it was my experience - that there is an emphasis on "difference." Interestingly, that is how "wa" is maintained - when your "place" is known, there is a way to fit you in.
On the other hand, I definitely felt "included" - and any violence I experienced in dojo settings was not due, in my experience, to anti-foreign sentiment. Some people just didn't like me.
I was quite deeply included in people's homes and lives for many years - my differences still emphasized and taken into "account" - but included I was.
One interesting experience. I believe I may have been the first non-Japanese to demonstrate at the Nihon Budokan in their yearly koryu embu. No, actually, there was a foreign student as part of a large entourage of Takenouchi-ryu, but I was going to be the lead - senior of a group of four of Toda-ha Buko-ryu. Some, at least, consider this the pre-eminent demo of koryu in Japan. I very much disliked demos at this time, and tended to avoid them. The day before the demo, when Nitta sensei turned in the final list of presenters, a very senior member of another ryu suggested that it would be shameful for the ryu that it was represented so prominently by a non-Japanese, that it also held Japanese up, implicitly, to negative comparison. Nitta sensei's response was to say, 1) that the affairs of our ryu were none of our concern 2) to call me up and order me - the only time she ordered me to do anything to demonstrate.
On another occasion, Nitta sensei, Ms. Kini Collins and I were to demonstrate at Shimogawa Jinja in Kyoto and Nitta sensei took ill. Kini and I demonstrated - it may have been the only time in Japanese history that the ONLY demonstrators in such an embu were non-Japanese. Everyone watched us very intently, to be sure, but in both direct and subtle ways, Nitta sensei was informed that we did right by the ryu.
So, even though I experienced a fair amount of bias and rudeness in my time in Japan, I honestly think far too much can be made of this. Stand-up people are accepted in budo society - even though your "differences" are not forgotten. And yes, some people may not - and some people may be rude or violent. But I honestly think more problems would happen on the organizational and administrative side than on the mat itself.