This has nothing to do with ideas. The site was used as a dumping ground for letters claiming responsibility^1, doxxing of right wing activists, calls for violent protest and so on. The whole thing is a little bit odd because in the past, this kind of prosecution has been targeted way bigger threats: Jihadists, Biker Gangs, paramilitary Nazi groups and stuff like that.

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^1 for what may be best described as "petty terror": Torched cars, smashed windows etc.