It’s not just social media - nearly every bit of media these people consume (TV, newspapers, commentary and social) is leading them down this road - they are on the side of “freedom” the others aren’t; they are the “patriots” the others aren’t; they are “the people” and the others are, well, the others. Only their proposals are common sense, even when they aren’t. Only they care about the country, even though in this case it’s not clear what country they are actually on about (England or Britain) and it’s fairly evident they are harming it by what they support.
As you say this is similar to what happened in the US, albeit of course we’ve already got around 30% of the populace who believe whatever the Tories and their media tell them, so we might even be further down the road of madness anyway.