Tying dissenters to recessive political sides in order to slander them as "extremists" or otherwise ethically questionable people.
Even though people are always divided along the "right vs left" or "conservative vs progressive" political spectrum, there is almost always a "mainstream" side whose values dominate mainstream culture and are therefore the most socially accepted, and an "alternative" side whose values are frowned upon by the mainstream and seen as socially questionable or even dangerous (this has nothing to do with which party is currently on charge). Therefore it is possible to manipulate public opinion into agreeing with determined policies by simply tying those policies to whichever political "philosophy" is currently the mainstream one or to the values conventionally associated with it; this is done by having mainstream political parties, journals or celebrities supporting those policies in the name of their values (or, more correctly, a highly warped interpretation of them); there is no limit to what kind policy can be pushed, or to what kind value can be used as its pretext, with the adequate amount of sophistry and rhetoric. On the other hand, it is possible to prevent public opinion from agreeing with ideas that threaten the status quo by tying them to the opposing (and therefore generally despised) political stance: in times when the accepted cultural values are right-leaning ones, dissenters are depicted as left-wing extremists, in times when the accepted cultural values are left-leaning ones, they are depicted as right-wing extremists instead; this is achieved by having mediatic attention selectively focused only on the members of the opposing parties, journals and characters who agree with those ideas (better yet if they're part of some extremist fringe group), and never mention the "normal" people who also do. Typical examples: Average mainstream depiction of dissenters and conspiracy theorists in times of "conservative" cultural dominance: "anarchics", "communists", "degenerates", "hippies", "junkers", "subversives", ... Average mainstream depiction of dissenters and conspiracy theorists in times of "progressive" cultural dominance: "alt-righters", "anti-semites", "incels", "nazis", "racists", "white supremacists", ... The continued rehearse of this narrative also causes a "Pygmalion effect" of sorts, where more and more dissenters are instinctively pushed towards the deprecated political side and vice-versa, with the added result of confirming the narrative itself and triggering a positive-feedback mechanism that makes their ideas more and more despised to the eyes of the mainstream public.