For the far right, anyone left of centre is a "Marxist" or a "socialist." Fear is a rallying cry for them and the fear of socialists and socialism has been built up for decades - it's an easy dogwhistle to blow to try to rally around them. They can't argue policy, at least not in good faith, so they stick to fear of the "other" - with Brexit the "other" is immigrants, with UK politics the "other" is socialists.
How anyone can say they'd back Boris's Brexit "for the good of the nation" after shitting all over May's deal... which many feel was less harmful to the British economy than Boris's deal - and that first deal was universally considered bad - it just requires a ton of mental gymnastics. But it's the same people that have been doing mental gymnastics since before the referendum, assuring themselves (and each other) that the rest of the world will abandon multilateral trade agreements if we do (spoiler alert: that's fantasy thinking) and that us leaving the EU doesn't significantly weaken our hand at the negotiating table for future trade deals (it does) - therefore they reassured themselves any short term hit to the economy was just going to be short term. They were "ripping the bandaid off."
It's hard to take any of the far-right Brexit brigade ideologically seriously either, because the goalposts keep moving. First we were promised there wouldn't be a hard Brexit, then we were told a hard Brexit is what the country voted for. And it shouldn't be surprising, since one of the "great minds" behind Brexit is Nigel Farage - a man who genuinely had power to push for the UK to have more power in the EU as a MEP, but instead used that role to collect money from the EU while not really representing UK interests at all and prefers using his time as an MEP to just be an irritating troll. And what's his fucking stance on Brexit? If it's shit for the UK, he's going to fuck off to America.
It's much easier to take the left-wing Brexit seriously - EU economic policies for member states and the austerity foisted on Greece are so much in line with many Thatcher era economic policies - it is a more ideologically consistent approach to Brexit. The counter point to that is that many of these legitimate concerns that ended up devastating communities and have led to Westminster funneling funding to London while neglecting most of the country, particularly the north, should have been taken more seriously then. And it's true - they should have. But it's been 3 decades of investing into this system. This isn't ripping a bandage off - it's going over a healed scar, saying you're tearing the bandage off... but first you cut yourself over the scar pretty badly and need to bandage yourself back up again. The easiest counterpoint to a left-wing Brexit argument is that... it's likely not going to be a left-wing aftermath for Brexit, because it'll likely come in led by Tories - it'll be to usher in a new Thatcherite wet dream. Because to Tories, the EU goes too far in business regulation, employment regulation, and ensuring that workers are adequately paid.