Imagine two houseguests who stay in your home. Guest 1 likes a lot of superficial things about your home. However within a day he starts complaining about many things. He doesn't like your food, your choice of furniture, your family's daily routines. He finds fault with several customs within your home and insists that you adopt customs he grew up with in his household. After a week, he returns back to his home anyway. Guest 2, absolutely adores your home and family. He goes out of his way to adapt to your lifestyle. A twist of fate causes him to end up living with you permanently. He gets along with people in your household. He works a job and contributes financially. He basically becomes part of the family. After a while, he begins to offer suggestions about how to improve things in your home.
Among the Gaijin community in Japan are two camps, conservatives and progressives. The former adore the culture and want to preserve it. The latter see Japan as backward in many ways, and seek to make Japan become more westernized. The thing is, neither of these camps have standing in my view, unless they become immigrants instead of expats. The expat is not deeply invested in the society. He has fun for a few years then goes home. The immigrant is deeply invested. He intends to live there permanently. He assimilates into the culture, learns the language, raises a family there, establishes a career, pays taxes, and often becomes a citizen and votes. You could say he has “skin in the game.” For that reason, native citizens care about his point of view and generally do not care about the expat.
Is this unfair to the expat or temporary visitor? If you were an American progressive, how would you feel about groups of Middle Eastern or South American migrants coming to the USA and loudly agitating for criminalization of homosexuality and more government funding for religious programs? Most likely you would find it unseemly. You might think, “Why don't they just go back to their own countries if they like their culture so much?” At the very least, you would likely hope that the American public will just ignore these interlopers.
No one is saying that the expat does not have a right to his opinion. We have all been houseguests at one point. After one night at my aunt's crazy apartment, I had A LOT of opinions about her lifestyle. However none of it was really life-threatening, so I kept my thoughts to myself. Similarly the expat can think whatever he wants and voice his views wherever he wishes. However people are more welcome to dismiss him, as he likely does not know very much about the native culture, and his views simply represent his own conditioned preference for the culture of his homeland. By contrast the immigrant has delved deep enough into the culture of his new home out of necessity. He is not on a vacation from his homeland; he is establishing a new one. Because he is more invested and likely better informed, his views are worth considering.
Japanese society will naturally evolve as Japanese citizens live their lives and make choices every day. I think that those foreigners that gain standing by committing to the country have a place in shaping that evolution. My advice to progressives is this: if you don't have standing, don't act entitled to have people care about your opinion. If you do have standing, focus your argument for change on how it will concretely improve things, not simply on the fact that “other countries do it, so Japan should too!!” To conservatives I would say do not blindly defend every aspect of Japanese culture simply because it is Japanese. All cultures evolve and change, including Japan's, sometimes for the better. Pick your battles. Focus on the things worth conserving.