My time in Japan lasted ten years, and for many reasons I consider it my second home. The degree to which living in Japan, fully immersed in Japanese language and culture, altered my life path and my mind itself, it cannot be overstated. The door for such culturally illuminating possibilities closes slightly with this news.
However, in that time I also observed my fair share of belligerent and oblivious Westerners, or even ones who didn't like Japan simply because it didn't accommodate them in some particular way.
These people need to have more of an open mind in order for Japan as a people to remain open-minded toward immigration.
(I was never a JET, but I befriended many who came and went over the years.)