The weirdest part is that this implies that “truth” - particularly that of history and current events - is determined by “mainstream consensus”. I read the original source to see if there was any clarification of what that means - whether “mainstream” is redundant in context or if it implies something else, like perhaps “non-mainstream people don’t get a say”, plus whether the consensus is of everyone or of experts or of leaders or whoever. None is provided, so I’ll assume “redundant” and “everyone” to simplify things, even if it feels like there might be some sort of “not everyone counts” involved here. Regardless, “what happened” is not an *opinion* and can in most cases can be objectively determined (within a degree of uncertainty, and not always with all the details); it’s not something which people just get to make up.
The description of Reddit as a symbol/haven of left-wing censorship (not in the OP, but in the original source) is interesting. Reddit in general skews younger and more liberal, though plenty of nonpolitical and right-wing subs exist. Reddit is community-driven social media, which means that the communities are free to silence you and kick you out if they think you’re being disruptive or really don’t like what you have to say. This is not any different from IRL/meatspace communities, and is not Reddit soft-censoring you. Reddit does ban communities which are sufficiently disruptive to other communities or which repeatedly and egregiously violate their rules, but virtually every social media does that regardless of political leanings, so there’s no reason to single out Reddit for that.
This reads like someone who spends most of their time in an information bubble, thinks that bubble is representative of the “mainstream”, at some point concluded that any differences outside of the bubble is “left-wing censorship of mainstream views”, and also has trouble distinguishing fact from opinion.