> Because it doesn't harm anyone.

Threats don’t harm anyone physically. Similarly, conspiracy to murder isn’t an actual murder until the murder is carried out. Calling for a genocide isn’t an actual genocide, but it’s hard to see what purpose it serves other than being the first step to enacting a genocide. There are plenty of other examples of speech acts rising to the level of criminality that no ordinary person would consider to be Orwellian.

> If censorship laws are all that's preventing genocide, it's not like people are going to go, "Well, we'd love to genocide that other group, but these pesky censorship laws, I guess we'll have to find something else to do..."

By this logic we shouldn’t have any laws, because people will always find a way to circumvent them.

> You accuse 4chan of allowing "absolutely reprehensible political views"

You are quoting a different user. My chief contention is that the sort of material you can find on /pol/ often rises to the level of incitement and that there isn’t anything wrong with prosecuting people for it. The same logic used to justify the criminalization of threats can be used to justify the criminalization of hate speech. The meta then shifts to inventing new or redefining existing categories of violence, sure, but this is just a slippery slope fallacy which assumes that there will be an endless tolerance for bad faith interpretations of an existing law. Outlawing murder has not led to the definition of murder becoming so expansive as to prohibit the general public from discussing the death penalty, for example.