I tend to think of $PUBLIC_FIGURE as a radical and an extremist. These terms usually carry a perjorative connotation. Similar terms include "fundamentalist" or "absolutist" and might also be defensible here.
To draw some of the personal sharpness out of it, one might argue less that they are these things, but more that they hold these views or positions or pursue a course that has this nature.
It might seem like a pointlessly semantic argument, but I think distinguishing the one from the other has a very good point. Distinguishing a person from some of their current, public attributes leaves more room for nuance, for recognizing that people change in their approach to the world and in their identity over time, and that they might continue to change in those ways. It is a more humane view, because it allows us to continue to see the person as just another person, rather than as an embodiment of an abstract cause. It allows us to work to preserve and expand our areas of common interest and agreement, rather than turning those commonalities into a shared but battle-ruined wasteland.