Libertarianism boils down to "I got mine, you get yours" which works so long as you live in a totally closed system. If you're a settler living alone on a frontier with no hostile Native Americans attempting to drive you away, Libertarianism makes perfect sense. Of course, so does anarchy.

But the minute you inject a contested road into that Libertarian paradise, you have a public good, which has to be protected and maintained through communal resources and "communal resources" is where Libertarianism falls apart. Who pays for the road? Everyone equally? But Joe uses it nine times a day and I only use it every other week! So does Joe pay nine times the taxes? But that will encourage Joe to cut his own private road which is going to scare off the bison we all hunt! And why do I have to pay for the defense of the section past the mercantile store when I never go beyond that? The mercantile store should pay for it and incorporate their fee into what I purchase from them so that other mercantile stores have reason to set up on a different road...

The basic idea of Libertarianism is that capitalism can do no wrong and anyone wronged by capitalism deserves to fail out of life. It exists functionally in an even smaller microcosm of success than communism. However, its philosophy tends to attract spoiled rich kids that don't understand and don't care that the society they live in thrives by protecting the disadvantaged from the advantaged. "Greed is good" is a Libertarian sentiment. Libertarianism is fundamentally intellectualized and codified selfishness and there are zero social or political models that don't protect against selfishness as their fundamental basis.

So "Libertarianism" is always "I got mine, you get yours" with varying degrees of "well of course we'll need an Army to protect my homestead against the savages but I won't pay one penny more in taxes" which basically means that any manifestation of Libertarianism is basically pure selfish anarchy with whatever sops the Libertarian has grudgingly agreed are vital to his own personal being. The idea that there might need to be taxes and laws to protect ideas and values that the Libertarian hasn't thought of is anathema.

Show me a libertarian and I will show you a smug, selfish asshole who thinks he understands government and society much better than he actually does. More than that, I'll show you a person who has long since stopped listening to people who do understand things better than he does... not because he's a closed-minded, selfish asshole but because he has "philosophical differences" with "mainstream politics."

And that is why Libertarianism is immoral and worrying. It turns the vice against which society legislates into a virtue and protects it as an asset, not a deficit.