There are people I have known who are schizophrenic (not saying this case at hand involves this specific illness). They had obsessions with various things and people. One with then Prince Charles and the Gov of PA, one with the Virgin Mary and with Jews. The latter may well have been violent, though I recall more cases of vandalism with him. Then there was a man I knew who was schizophrenic, though he was violent, and would physically attack women.
Was former Ambassador Madeline Halfwit a dangerous extremist? She believed Bush kept Osama on ice to reveal his death when needed for political gain. Is Hillary a dangerous extremist, she still says Russia helped Trump steal the 2016 election.
Extremist, Radicalized, I reject those labels.
I don’t think the fit.
I also think as you outlined everyone is different even the mental health issues.