It's challenging because the optimal strategy for converting an individual is not necessarily what's best for society as a whole.

Risking Godwin's law, imagine the extreme case of Hitler. The best strategy to convert Hitler may well be Jewish people befriending him, rather than confronting him. But in the meantime, Hitler is radicalizing others and committing genocide. At some point, it makes more sense to just assassinate Hitler (or deplatform him, or depose him, etc.) rather than trying to save him.

No, it doesnt. Responding to mere speech with escalation or violence has not ever worked in the responder's favor. It has instead fueled coups and revolutions (like the American civil rights movement).

Killing someone for their ideas sends the wrong message and grants them more legitimacy than anything. You elevate them to the same status as Jesus Christ, whose popular namesake religion is predicated on sticking to your beliefs in the face of any and all consequence.