Indeed jib71 captures the "moral" of my story quite well. Unless you know for sure that your other tour members are going to "behave" throughout the trip, and are the kind of people that are so respectful of other's cultures that they are happy to constrain themselves to a Japanese bus tour for more than a day or two, then go ahead. Otherwise, jib71's suggestion that JTB be used sparingly at specific cities or sites is a good one. JTB (or any good travel agency, for that matter) can help organize more or less a "self-guided" tour, where there is a lot of free time and specific guided tours are contracted in advance. That's what I did first time I went to China 20+ years ago, and I thought it worked pretty well.

Just a corollary story to the Pickles Magical Mystery Tour, a few months ago my mother and my cousins came to Japan and we went to Kyoto for sightseeing. We were at one of the Daitokuji inner temples, place was pretty empty, so it was nice. Then, from the side, the temple abbott appears, guiding a tour group of a couple dozen Japanese middle-aged couples. The abbot was explaining the meaning of the rock garden, and his every comment and explanation was accompanied by unison "so desu nee", "naruhodo", "so desu kaa", "eeeh" from the tour group. It was so stereotypically funny my mother took a video of this scene for posterity.