Hitler didn't "get over 6 million people to follow along blindly and not fight back." By the 6 million, the meme-maker presumably means the 6 million Jews who died in the Holocaust, and they mostly did not follow Hitler. There were some German Jews who did support Hitler, thinking that they could prove that they were Good Germans. But they were few. Before Hitler came to power (if you don't vote, you can't complain!), the Nazis relied on street violence through their thugs to intimidate their opponents, not all of whom were Jews. After he came to power Hitler passed laws depriving German Jews of their rights as German citizens; these were enforced by more violence, this time official state violence. Many of the 6 million weren't German -- they were in countries the Germans invaded and controlled. They didn't follow Hitler either.
The racists who share this meme think that German Jews could have resisted successfully if they hadn't been disarmed. (It's a popular racist Israeli fantasy, too.) That's doubtful, since Jews were a tiny minority in Germany: even armed resistance would have been put down brutally, and would have been used to justify Nazi propaganda against Jews as a threat to civilization. By contrast, the white American racists who share this meme are among the overwhelming "racial" majority in the US. They are generally armed, and no laws have been passed that would change that. African-Americans, who are an oppressed minority in the US, have often resisted, sometimes but not always violently, but the white racists who made this meme don't approve; instead they see their dark compatriots as a threat to them.
The message of the meme, then, is that HitlerObama is leading white Americans, whom he has disarmed, down the primrose path to their/our ultimate elimination. The person who shared the meme from The Comical Conservative remarked, "The even more scary thing is that almost all 'western' nations are on that path, threatening something much much worse than WWII. If we are truly honest, WWIII is already underway." Evidently he didn't think about its content either. So why did an anti-racist, politically left person approve this nonsensical piece of racist propaganda?
From what the friend who liked the meme on Facebook told me, she assumed that "more than 6 million" could not refer to the Jews, presumably because the iconic number for Jews killed in the Holocaust is 6 million, not "more than" 6 million. I understand this, since it gave me pause when I first saw the meme. Probably she read it in the light of what she knew of the person who brought the meme to her attention, another progressive. Someone else, commenting on our exchange, said that he'd seen the same meme invoked against Donald Trump and his racist followers. I think this confirms that they're misreading it: who would expect Trump's white racist fans to "fight back" against him, any more than one would expect German anti-Semites to "fight back" against Hitler?
I'm also put off by "almost all 'western' nations are on that path." Why "western," and why in quotes? Non-western nations don't have a good record either. The strange thing, for a person as misanthropic as my friend, is that she can look at human history and see Hitler and the Holocaust as aberrations in kind, rather than in degree, let alone affect to be surprised by them. Anti-semitism was deep-rooted in Germany, as in Europe generally; the mechanization of death began not with Zyklon B but with heavy artillery (remember that the American Civil War was the bloodiest war in history in its day), if not the invention of gunpowder; Nazi race science drew heavily on American eugenics, as well as the extermination of our pre-Columbian peoples -- who were no angels themselves, but the wrongness of mass slaughter is not dependent on the moral purity of the victims.
No doubt I'm overreacting; I don't see that as necessarily invalidating my response. It's legitimate to be appalled by the eruption of white racism in the US. Racists have clearly been emboldened by Donald Trump's strutting about; comparisons to Hitler are not entirely out of line. But simple Us/Them divisions aren't going to help, and we need to think about the propaganda we ourselves appropriate.