I don't understand "No Platforming" as a verb here... I infer you mean something like calling for the removal of Nazis from Twitter? I think there are some aut

I don't understand "No Platforming" as a verb here... I infer you mean something like calling for the removal of Nazis from Twitter? I think there are some authoritarian leftist activists, but I doubt it's a particularly representative sample of the overall category you're thinking of when you mention leftist activists. I think you're just drawing the wrong conclusions from whatever you've read of Mill. Section 44 from the essay: Undoubtedly the manner of asserting an opinion, even though it be a true one, may be very objectionable, and may justly incur severe censure. But the principal offences of the kind are such as it is mostly impossible, unless by accidental self-betrayal, to bring home to conviction. The gravest of them is, to argue sophistically, to suppress facts or arguments, to misstate the elements of the case, or misrepresent the opposite opinion. This also comes after Mill has walked a fine line in section 38 describing how Christian morality must be both questioned, and augmented as some kind of intersectional morality along with other faiths. Whatever reading of Mill you have that makes you think leftists would disagree with it...