Okay but if you engage them and make people see that they are not only radical but also idiots, that defuses the problem pretty effectively
if you could do that in a way that somehow flawlessly convinces everyone, sure. what happens in practice though is that, when you give an ideology a platform in public policy, people entertain the ideas and become accustomed to them. people don't go whole hog on promoting radical ideas from the start because they aren't oblivious to mainstream politics. by engaging them in public debate, you're giving them the tools to slowly shift the overton window in their favor.
besides, people are already numb to the contention that ideas can be immoral. calling someone tribal isn't incredibly compelling when juxtaposed with pretty-sounding white supremacist ideology, even if it's true
