As opposed to the British Empire and, essentially, everyone else who could?

Most ideological death marches I have witnessed in my party have also been accompanied by lack of debate due to unilateral threats of de juro or de facto expulsion by some sort of manufactured consent that seems to come from nowhere.

Aside from defending free expression as a matter of principal, yes it actually does work over time.

Except during a brief, half-baked spell of McCarthyist schizophrenia in the 50s, the United States, during the whole course of its massive cold war with the USSR, never saw fit to ban support for communism, the publication of communist literature, open talk in support of communism, or even the existence of an actual communist party inside its borders (thanks 1st amendment). Despite this, said ideology simply having to compete in the marketplace of ideas and practical reality, slowly turned into more of a running joke than any real threat in any meaningful sense to U.S society.

Bear in mind the obvious too: once you create the legal right to legally repress insidious ideas, it's a very small leap for successive administrations to also start banning "insidious" ideas, meaning anything they happen to not like out of some self-serving convenience. In the west, there has been, since 2016 in particular, an intermittent fever of force-fed fears about the so-called dangers of misinformation, one promoted by media and politicians both, only for that very same idea to be used by one robust list of real authoritarians specifically to crush disagreement with their particular variants of nonsense, mendacity and propaganda.

Solutions however won't be wholly accepted by the ruling class favored by the current ideologies since these "insidious ideologies" oppose their position and power and "mandate of heaven". The ruling class can risk subverting themselves or surrendering power.

And yet, there is some truth in ascribing a lot of violent deaths to communist circumstances, at least in the last two centuries. The fact that, as opposed to Nazism, in Communism killing others was never a direct aim, in practice human life somehow lost much of its value and people were dying in various ways, both individually in prisons etc., as well as en masse like in Holodomor.