Libertarians need the alt-right because the demographic changes cause by mass immigration will assure that you will permanently lose on most of your major issues. Whatever pet theory you have to why this is the case is really irrelevant...increasing 3rd world immigration will bring increasing 3rd world dysfunction into 1st world countries. Identity politics will become the only politics because the different demographic groups have no common identity or history. Like in many diverse societies, politics will become an ethnic spoils system where differing groups demand more free shit and special privileges from the government while crushing the middle and upper classes with punishing taxation until the whole system collapses. Competing groups who view each other as hostile aliens will fight for state power in zero-sum fashion while promising ever more freebies to their tribe with no regard for long-term consequences. All this will do is work to increase centralized state power exponentially and further bloat the bureaucracy, as it becomes more craven and corrupt.
Listen, the world is full of people that don't give a flying fuck about liberty as you might understand it. They just want material comfort. Many more enlightened lower class people realize that if you don't like whatever law, you just break it, it's that simple, so who gives a shit about runaway regulation? This small government, limited regulation autismo is largely a white phenomenon, that is an inherited legacy of traditional American mythology surrounding the 1776 revolution and Enlightenment thought in general, that many non-whites, immigrants especially, don't identify with and don't give one flying red fuck about. Take a look around at any Libertarian gathering and report back to me the racial makeup of the attendees. And yes, there's always exceptions, I'm talking about general trends. Problem is, democracy is winner takes all and general trends determine the outcome of your politics which determines the outcome of your society.
The drug war, however, is an exception to this. The demographically induced leftward shift (and yes, the kvetching of the libertarians) may end the drug war as we know it in a decade or two. I'm no fan of the drug war, vice is it's own punishment, but drugs are given WAY too much importance in the grand scheme of things by libertarians. They focus on the drug issue because it's easy...it's a naked example of the government persecuting peaceful people for consensual crimes. I'm on board that this is an obvious hypocritical evil, and a massive waste of resources. Still, this being your only hill to die on is ridiculous...is illegal drug use so important to the health and happiness of the average person that it warrants this much attention? Let me ask you this...if you achieved your Libertopia of all drugs totally legal, how would the life of the average illegal drug abuser (already a small subset of the population) realistically change? Yes I could by crack rocks at CVS instead of the corner hustler, woopedy fuckin doo. If you're so inclined and have a modicum of discretion, drugs are very easy to buy and use without police harassment. Well what if you're a drug dealer? Could get a hefty prison sentence. Well, drug dealers should be thanking their lucky stars for drug prohibition, because if there was no risk of incarceration, they would never be able to compete against GloboCorp Dope Distributors. Now you've just removed thousands of independent sole proprietors practicing agorism in favor of corporate oligarchy where liquor store clerks making minimum wage hawk heavily taxed tweaker fuel.
I also think that blaming inner-city dysfunction on the drug war is laughably naive. You really think that Detroit would just become a modern marvel of prosperity if it's denizens could buy black tar at Costco? Give me a fuckin break. If anything, removing one of the last viable side-hustles from a poverty stricken and embittered populace would probably have them grasp at even more anti-social methods of illicit income than drug dealing, even though battles over territory are a real problem.

This also begs the question, why are universally applicable drug laws only hurting black communities to the point that this totally defines their socio-economic plight? Do minorities just LOVE drugs that much? You're not realizing the extent to which disparities in what we might define as social pathologies follow African majority societies EVERYWHERE they exist around the globe. The richest black neighborhood in the U.S. has more violent crime than the poorest white neighborhood. There are globally evident IQ disparities amongst different races independent of income levels or socioeconomic status. Lower IQ's do highly correlate with all manner of adverse life outcomes, including the odds that you will do time in prison. To what extent this is a cultural artifact or is genetically determined is not really relevant to the outcome, but it does no one any favors to avoid the overwhelming evidence of cognitive/behavioral racial differences in favor of glib explanations for disparities that invite even sillier faux solutions. It makes you rely on vast international conspiracy theorizing and ad-hoc rationalizations as an explanatory basis for your religious-like faith that all human groups are the same in ability, potential, etc. This is an extraordinarily shaky foundation that will continue to be eviscerated by the alt-right.