DY – When a “Chochom” breaks basic din principles, and then in the same letter claims that others did what he accused them of (when it is well known that they didn’t and he could have asked), then that individual is not Da’as Torah, no matter how “smart” he may have been. When he shows his Negius publicly, you can’t say he isn’t Nogaiyh B’davar.
That being said, it’s a very different story for a Talmid Chacham Atzum like Rav Chaim (who says himself that he is not a Posek). There it is a matter of understanding that the answer is based off of prior poskim, and has to be understood in that context. One of the examples that I like to use is Rav Chaim’s Pask that one must wear a hat for davening. This really is different for the Yeshiva Bochur (who goes in the street with a hat) vs. the Baal HaBos (who does not). The yeshiva bochur MUST wear one (as Rav Chaim Paskens), since that is “Derech Sheholchin Brechov” (As the MB says), but not one who goes out without a hat.