I read Capital and know Marx's argument quite well. I'm speaking more of Communists today who get spooked when someone says "for fuck's sake, just hang the bankers", and in some places I've been shamed for even insinuating that the banking families are bad and have nefarious intentions.
No one who has worked for long enough needs to be told that the boss is stealing value from you. It is self-evident that the system, in aggregate, can't afford to pay workers as much or more than what they produce. People, for the most part, aren't so stupid that they need Marxism to tell them they're getting ripped off.
I've tried to explain that to ordinary people who are sick of the system and look at the top of the system (the banks, the megacorps, and the state), that the reason the first and last of those things is so big is because capitalism as a system needs it. But, I also believe it's a cop out to say "oh, the capitalists just want to make money", and ignore the very real intentions of the people at the top. These people are not innocent bystanders or crudely self-interested. They have plans, plans that the people at the top have generally agreed upon and have pushed through ideology, that involve something more than just maintaining the system, or even their own rule.
Because the people within the fascist movement who have influence benefit from deregulation and capitalism as it is, obviously. If they're not directly in strong positions in the economic system, then they're usually hangers-on whose status in society is dependent on sucking up to capital.
That the poor fucks who follow the leaders can't see the leaders' obvious contempt for them demonstrates the power of ideology to retard people and reduce them to slavering animals.
Seriously, once people get sucked into the conservative propaganda vortex and are isolated from meaningful roles in society, the ideology really does its work, reinforced by a steady stream of propaganda. Trump's retarded speeches were not meant to be taken seriously by anyone - they are meant as a statement of force, like an ape beating his chest in a show of dominance. The hard-right base you're thinking of has been so degraded that it's difficult to talk to them as if they are actually people, because in a lot of ways, they really aren't people any more, not in any sense that is recognizable or palatable in public life.
For a lot of reasons, socialists don't have a use for these people, and has rejected them in the unusual event that they are politically neutral or even willing to align with socialist causes. Liberals obviously have no use for them.
The best you can hope for with them is to get them to hate the retarded ideologies fed to them by the right more than everything else. This should not be a difficult task, if the left (or even the center) were able to critique rightism with meaningful language. Usually, the most the left can muster is that the rightists ideology is stupid, or (far more commonly) the rightists ideology is mean. There's little stomach to really dissect just how EVIL the ruling ideology is, and that much of the direction in the present society is deliberately and willfully taken to maximize the oppression and suffering of people. (For one, in order to make a meaningful critique, eugenics and population control must be criticized and utterly rejected as the evil that they are, and no one is going to do that for obvious reasons; further, in U.S. law at least, eugenics is still the unquestioned law of the land, and libs and even socialists pretending that "eugenics is over" doesn't help you any.)