No, and nor should you. But Marx's argument is pretty good.
I am interested that the historical occasion you give for revising his principle is the second world war and the fight against fascism.
You seem to be saying that it is fascism that is qualitatively new and demands a different approach to freedom of speech.
But could I suggest another reason why ww2 would be seen as a turning point?
It was WW2 that first saw the third international unite with the allies in the war against Germany. Embracing the allies war effort as 'the people's war' led the comintern to a collaborationist policy with British and American imperialism. The political independence of the working class movement was sacrificed. Identifying with the state made the principled defence of freedom of speech redundant. Instead the state was looked upon (in defiance of all reason and experience) as the guarantor of liberty, instead of for what it was, the greatest danger to liberty.
It is doubly perverse to cite fascism as an instance in which bans on free speech are justified. Fascism was characterised by the suppression of free speech, book burning and the suppression of all political opposition.
Furthermore, the SPD often made the mistake of demanding state action to limit the fascists' freedom of speech. Mobilising working class support for such bans the SPD gave the repressive laws a measure of respectability that they did not deserve.
Time and again the German state used the laws against freedom of speech to suppress the left, while refusing to use them against the right. Why? Because the right was the state's ally.
And after the SPD put the laws into the statute book under which it was liquidated, here we are again demanding that the ruling class protect us from 'hate speech'.
How naive can you get? Turkeys for Thanksgiving? -- Jim heartfield