Please pardon my departure from your viewpoint but your portrayal of Meschichists is inaccurate. When I myself was investigating the matter of saying yechi after Gimmel Tammuz,, I consulted with R. Leibel Groner,the secretary of the Lubavitcher Rebbe. He told me that personally he does not say yechi but that he does say yechi haMelech because that is the version that he heard from the Rebbe. However since the custom has developed that people say yechi adoneinu ,it is a legitimate expression. Another thing, some of the people that are meschichists represent a veritable who's who of Chabad including R.Yitzchak Ginsburg ,two members of the Crown Heights Beis Din and R.Yehuda Kalman Marlow z"l,its former av beis din.Strongly recommend that you contact R. Eli Turen who was instrumental in getting Rav Aaaron Soloveitchik to write the statement in the Jewish Press. Kol tuv.