I think the important distinction for BI is between authoritarian and anti-authoritarian, not between left and right. The two dichotomies are orthogonal. Anti-authority/pro-liberty types typically require only a brief explanation of BI before enthusiastically signing up; this is true of principled libertarians as much as it is of the counter-culture. As for authoritarians, I don't think the UBI movement has yet had to stare into the howling abyss of left-wing authoritarian hatred of BI and all it stands for. Not everyone who is allergic to individual independence and self-rule is a right winger. Many of them are working class. How can we ask a member of the working class to support SLACK? So yes, I agree with you; but only because I think that right vs. left is not the dimension that counts for BI.
These frames seek to obscure the relevance of left-right analysis to certain right-wing politics in order to support the status quo and the incumbent-elite interests aligned with it. Of course, market libertarians like to pretend they are "beyond left and right" (or try to market themselves with distracting neologisms -- independent! upwinger! dynamist!) because they can no more prevail with majorities than conventional Republicans can if they are too explicit about their actual alignment with the interests of plutocratic minorities.
Market libertarianism is a right-wing ideology -- it claims to be anti-authoritarian while endorsing corporate-militarism, and to advocate non-violence while endorsing contractual outcomes as non-violent by fiat whatever the terms of misinformation and duress shaping them. Since "fiscal conservatism" always cashes out in de-regulatory and privatizing schemes dismantling the legal/welfare affordances of social equity and cultural pluralism this means that the "cultural/social liberalism" always proclaimed alongside the "fiscal conservatism" has no real substance.
It is no accident that the anti-authoritarianism of market libertarians always plays out as hostility to almost all government except for armies and police to keep the wage slaves from revolting against their plutocratic masters. It is also no accident that market libertarian arguments only impact actual politics when they provide selective justifications for GOP positions.
People manifestly mean different things by basic income advocacy depending on whether they are coming from left or right, but it isn't exactly surprising that someone who falsely imagines right-wing libertarianism to be beyond left or right would imagine basic income advocacy figured through a libertarian lens to be the same.
The commenter declares "the UBI movement has yet had to stare into the howling abyss of left-wing authoritarian hatred of BI and all it stands for" -- but the reason for this non-event is that the howling left-wing authoritarian abyss conjured here is a classic paranoid fantasy of the reactionary right. In this it is not unlike that slip-up about "working class" folks "allergic" to "independence" -- ooh, just smell the makers-v-takers race/class politics of "liberty"!
I'm sure Stalinist industrial-militarism and Maoist feudalism will leap to libertopian minds at my dismissal of these reactionary fever-dreams, but it really isn't difficult to grasp that the totalitarian impulse is a right-wing one, once you shed the re-mapping demanded by the World's Shortest Political Quiz. If you can grasp that Nazism was a movement of the right despite the word "socialist" in the logo it shouldn't be that complicated after all to trouble too slick an identification of the left with the gulag either. Neither is it so much of a leap to grasp the left impulse is essentially democratizing work toward equity-in-diversity once you set aside market fundamentalists pieties and the GOP corpse-cold Cold War playbook.
Comparably fantastical is the commenter's confident assertion that "pro-liberty types typically require only a brief explanation of BI before enthusiastically signing up." Yeah, except when they don't, which is pretty much always. Sure, a few market fundamentalists have tossed out thought-experiments about basic income when they were looking for a chance to score rhetorical points (what they mean by "signing up") about how awesome it would be to demolish the New Deal once and for all, but they never want to actually do anything (what it should mean to "sign up") to end wage slavery, eliminate the precarity draft, or secure informed non-duressed contracts. When have they "signed up" to do anything so jack-booted socialist as all that otherwise? When have they made their actual cases on such terms anyway? Attributing such motives for the occasional right-wing pseudo-scholarly foray into basic income thought experiments seems pretty far-fetched.
No doubt I am being biased, tribalist, immoderate, unreasonable to ask anybody to face these awkward facts.