One of the aspects of living in a foreign country and Japan in particular is that you have the chance to present yourself as an authority on whatever you choose to expound upon. When teaching, I overheard plenty of gas bags who loved nothing more than to "teach" by telling students "the truth" about whatever. Sometimes, the things I heard people say were so ridiculously wrong that it made me cringe, but students never challenged the assertions that their idiot teachers made. The largest part of the reason they did this is likely that they felt that they couldn't speak with authority on the topics the teacher pretended to know so well. Another large part is that the students are always at a disadvantage linguistically and can't express sophisticated notions well. And, yet another is that Japanese people don't operate under the misguided notion that their opinions are equivalent to facts as many Americans (and other Westerners) do. Finally, Japanese people out of modesty, politeness, and a higher concern for safe-guarding the relationships they have with people will often opt not to argue counterpoints.
It is easy in Japan to feel like you are smarter than you really are because you can say pretty much anything and have your ideas validated with a nodding head. It can be immensely gratifying to the ego to feel like you're an authority on anything of which you speak because you are dealing with people who either can't disagree due to lack of cultural experience or won't because of their cultural inhibitions about doing so and I will miss that sweet illusion.