[shirakawasuna]

An analysis of what is efficacious for opposing "extremism" is pointless without also looking at the cause(s) of that "extremism" or being able to identify natural experiments.

Natural experiments: looking at Germany and noticing that there are still lots of Nazis doesn't mean those interventions were not effective, as you don't know what would've happened using other regimes (or just doing nothing). You haven't tested the most basic alternative hypothesis that would confound using this data in this way.

Causes: this is a big can of worms, particularly on a forum where "politics" is frowned upon, which really means that anything non-normative that could cause significant disagreement is frowned upon. But unless you can identify driving forces of, e.g., Nazis and their recruitment, talking about effective interventions is premature and reductive.