I believe he's talking about punishing the overt act of publishing this large manifesto and the negative consequences that flow from it. Not the thinking or discussing his views.
While one can tolerate people referring to it as a manifesto for the sake of clarity, since his name is not common knowledge and there is no other catchy title associated with it, it's not reasonable to use that language to imply that what was written is actually a manifesto by the dictionary definition of the word.
A manifesto is a published verbal declaration of the intentions, motives, or views of the issuer, be it an individual, group, political party or government.
That is quite clearly not what the author's piece actually is.