Why shouldn't we hear what nationalists have to say? Who gets to decide what is a conspiracy theory? They're not all as simply false as flat earth. Keto in the low-fat 90s would have been a conspiracy theory and a culture of censorship would have killed it.

We need many groups of people believing different things and civilly arguing for what's correct. We don't need de-platforming or cancelling - that can only lead to groupthink and groupthink is incredibly dangerous: see the housing crisis or the Nazis.