DY, by voicing one’s opinion against a pesak someone received one risks being exposed a someone who does not know the diference between an alef and a swastika.
Lilmod, it is prohibited as LH to go straight to a public outcry. First you have to speak to the individual privately. In this case the Committee to Find Blemishes in Others (to use Rav Aviner’s term) is second-guessing the Secret Service, who know their business (and anyone with even a modicum of intelligence who saw the videos of what went on in the streets knows that they were right) and the rav who paskened.
Joseph, as it is a rabbinic prohibition there is flexibility. There are many heterim for someone who is karove lamalchut. A certain jailer who concealed his Jewishness so that he could save Jews was deemed by Eliahu to be worthy of Olam HaBa, according to the commentators without having to first go through Gehinnom (Taanit 22a). Presumably he had to go to the local bet a”z to keep up his disguise.