I am not familiar with this person, nor the matter, but from a quick web search, I found one of the reasons for the rescission of his status was based on his past Nationalistic statements and support for that cause.
In one widely circulated video, Navalny compares Chechen rebels to "cockroaches" and suggests that a pistol is the best way to eliminate them. In another video from 2007, Navalny espouses strong nationalistic views, saying, "We have a right to be (ethnic) Russians in Russia. And we'll defend that right." And, his support for Russia's 2014 annexation of Crimea, which was widely condemned internationally.
(note: most of the above can be found on NPR)
In response following the request to provide specifics about the "past comments", Julie Verhaar, Amnesty's acting secretary-general, referred to speculation surrounding the decision on Navalny, saying it is "detracting attention" from the organization's efforts to win his release.
"This distraction only serves the Russian authorities, who have jailed Navalny on politically motivated charges, simply because he dared to criticize them," Verhaar said.
"We note that some of Aleksei Navalny's past comments have been actively used by his opponents to discredit him," Verhaar added.
Amnesty International says it uses seven criteria to decide whether someone is a prisoner of conscience, determining, among other things, that the person "has not used or advocated violence but is imprisoned because of who they are (sexual orientation, ethnic, national or social origin, language, birth, colour, sex or economic status) or what they believe (religious, political or other conscientiously held beliefs)."
It is your call.
Follow up (Edit on 8 April 2021)
The quote below is excerpted from Amnesty International's Statement on Aleksei Navalny, to reflect/echo the statement made by Julie Verhaar in response to NPR that was cited above.
In closing, Amnesty International stated:
"*The fact that Amnesty International decided not to refer to Aleksei Navalny as a POC has no bearing on our insistence that Navalny has been unlawfully detained, and subjected to state-sponsored harassment and prosecution for exercising his right to freedom of expression.
Our ongoing assessment of past comments made by Navalny is unrelated to our position on the Russian authorities’ intensifying and brutal crackdown on human rights - including the arbitrary detention of Navalny - which we condemn in the strongest possible terms.
However, we recognize that the poor timing of this internal decision has unintentionally distracted from the campaign for Navalny's immediate release. We deeply regret any damage this may have caused to the campaign to free Navalny, as well as the distress caused to Navalny and his many friends and supporters.
Speculation around our internal decision has detracted attention from the mounting human rights violations being committed by the Russian authorities, and from our core demand that Navalny be released. The controversy around Amnesty’s use of the term POC has been weaponized by the Kremlin, against us and against those who are expressing critical views against the Russian government.
There should be no confusion: nothing Navalny has said in the past justifies his current detention, which is purely politically motivated. Navalny has been arbitrarily detained for exercising his right to freedom of expression, and for this reason we continue to campaign for his immediate release.*"
End of Exerption
Interested readers can read the full document here, https://www.amnesty.org/en/latest/news/2021/02/aleksei-navalny-prisoner-of-conscience/