^If, if, if. The meaningful question is, is it likely? What are the odds that some charismatic megalomaniac looking to start trouble would pick that particular issue to stir people up over?
It doesn't have to be a charismatic megalomaniac who'll make that argument; that's not the case now. Sizable double-digit percentages around the world--including inside the United States--believe that the United States government either allowed the September 11th terrorist attacks to take place or actually engineered them, all as part of a grand conspiracy aimed at subjugating the oil-rich Middle East in order to secure its global hegemony. Never mind that such a conspiracy would be absurdly vulnerable, requiring as it would at least thousands of people working in any number of competing agencies--and any number of competing countries!--to keep quiet about this absurdly complex and occasionally self-contradictory conspiracy for years on end. It helps them give order to a messy and chaotic worldview, and that's all that matters to them. It doesn't matter if it's convoluted.
Blaming humans for the Borg just doesn't cut it as a propaganda tool, because it's not straightforward enough. It's also hard to justify when the immediately evident fact is that humans played a key role in eradicating the Borg once and for all.
Comparisons to Weimar Germany have been made elsewhere, but they're absurdly optimistic. For all the post-war chaos Germany was a reasonably functioning state, with an economy that was intact despite indirect war damage and reparations and a civilian population that hadn't been systematically slaughtered to the point of causing regional depopulation. Europe after the Second World War would be a closer fit.
The Federation's neighbourhood has been very unstable lately: Even before the Borg came, the Klingonshad a history of fighting dynastic wars that saw the First City come under bombardment at one point, and a Romulan subject race assassinated the Senate and eventually triggered the ancient Star Empire's collapse into two competing entities. Throw into the annihilatory strikes inflicted by the Borg on the different civilizations in the neighbourhood of the Azure Nebula and you've got a mass of trillions of people living amidst ravaged economies, governed by increasingly unstable governments and living in societies subjected to who knows what traumas.
It doesn't have to only be traditional Federation antagonists who could be upset with humans, not after the damage inflicted. I'm reminded of how after the Second World War, the peaceable Dutch were suddenlywilling to annex and ethnically cleanse large areas of northwestern Germany. I can imagine Rhandaarites, say, wanting to know the ultimate reasons explaining why their homeworld is now a waste. Any number of nominally friendly populations--Vulcans being upset with the obliteration of their capital, Risians wondering if their species will even survive as a distinct population, Klingons looking to avenge their many dead--might be susceptible to anti-human memes.
In the end, it might not even have to relate so much to the origins of the Borg as to humanity's reactions to the Borg. We know that the Breen Confederacy's ambassador blamed the visibly human Federation for provoking the Borg with its expansionism, and it's not unreasonable to bet that a lot of people now think the human Janeway's destroying the transwarp hub was a stupid provocation of a hugely superior and relentless foe. The idea that human carelessness is ultimately responsible for the 63 billion dead could be equally convincing.
That's the big headline, the sound bite that the listener can easily grasp. And that's going to be more effective for propaganda purposes than some convoluted history lesson that can, at best, only feebly implicate humanity in the Borg's distant origins.
In Book III, after he learned of the Borg's partial human origins, Picard felt that one reason he succumbed to the Collective back in TBOBW was that it possessed a kindred human soul. That's significant. If people could portray the Borg incursion as the final phase in a human-on-human civil war that happened to kill huge numbers of non-humans ...