The word "extremist" with no further qualifiers is pretty useless, as it is a description of something relative to the average and thus something can change from being non-extreme (normal) to being distant from a new normal only because everything else moved but that being described remained still… or vice versa.
It was e.g. for a very long time extreme positions to be for abolition of slavery/for parliamentarism/for women's equal right to vote/for equal LGBT-rights, etc,
but then the average/normal opinion of society changed to being neutral and then to those remaining at the previous normal positions now being the only extreme position remaining, as the previous "extreme" positions are overwhelmingly considered the only socially accepted ones.
So generalizations like "all extremism" is probably not what users intend to describe.
Just saying… consider being more specific.