Earlier quoted context omitted.
As a French living in Japan one of the things I quickly learned is that if I complain about something while showing even a hint of anger or annoyingness, my interlocutor will take it personally, even if he/she is not involved about the thing as well.
Was you complaint about something related to Japan or the life there or the administration? Japanese people very easily feel compelled to defend their group, because if not they are often treated as "anti-japanese" by the most right-wing (which are the most vocal) of their relations/neighbors. This in turn leads to a lot of self-censorship.
I don't think it's about their opinions, it's just a language you have to be more polite in. Doesn't feel any different from the South or UK to me.