Maybe not everyone is looking for the best ideas, and instead will buy the ones that make them feel good.
I know I've covered this before, but it bears repeating. There are several assumptions inherent to capital "L" libertarianism that simply do not hold up under scrutiny and history, and inevitably result in its failure.
If you've paid attention over at Eric Raymond's blog, you'll also see a display that only recently shocked a libertarian-oriented economist in a debate because, at least on the academic-economic side of things, they had not considered the free movement of people on markets. Namely, a number of hard core libertarian types arguing against restricting immigration because of course libertarianism requires the right of free movement and de facto open borders.
Incidentally, this is yet another position that Eric has moved closer to something like the "right wing" view against his earlier assumptions. And of course, the materialists (leftists and libertarians) had to dog pile on him. God forbid he point out that "right of exit" doesn't imply a "right of entry" anywhere else. Or that not all immigrants are a net gain. Or when someone else points out that even taking the "good" immigrants furthers the decent of their home countries into shitholes.
Here are a few points that many of the pro-immigration side missed, some of which Eric also misses to a degree.
Libertarians refuse to recognize any kind of shared social contract or communal property other than the transactional. While I personally am skeptical of "propertarianism", the one thing it does have is a model to work with intangible things like community social fabric as something that exists, and that people are willing to defend.
Without these shared intangibles that everyone has a stake, skin in the game, to defend, there is absolutely no reason why some guy wouldn't sell landing or passage rights to invaders in exchange for benefits, or simply being left alone. Oh, sure, he may have a contract with the local arbitration and dispute board, but if the invaders win, that's not much of an issue, is it?
Regression to the mean - One thing Eric skips over, is that you can have a high-IQ person come in, but that doesn't mean his family is. That also doesn't mean his children will be, for if he as an individual is smarter than average, his kids may be as well, but very likely, smarter than average or not, are closer to the average of the culture he came from.
Communal Assumptions - Driving in DC and Miami sucks. One of the reason why is because so many people come from so many different places, and I'm not just talking other states, but other countries, that there is a very limited mutual understanding of behavior at intersections, regarding lane changes, and so forth. As Putnam's study showed, and he couldn't get the data to say otherwise, people from different cultures living in close proximity didn't trust each other, and even reduced trust within the monocultural groups.
Also consider communities, with the examples of wheels and indoor plumbing, things that can be done and maintained at a very low tech level and would vastly improve life in Africa and India, that nevertheless do not. What kind of assumptions will they bring with them?
Those fancy touch screens? Do you want to order after someone with third-world hygiene practices?
Miami feels foreign where Halifax, NS, CA, doesn't, not because of the spanish signage and prevalence of spanish being spoken, but because of the attitudes, and the displayed lack of trust in everything down to security enclosures around front stoops and doors.
Assimilation - to the degree it was happening, it isn't. As even Eric points out, to whatever degree we have had people assimilate in the past, we are not expecting that anymore, and the communities are not assimilating. As to successful assimilation at slower immigration rates, over the years I've come to disagree with foreign cultures assimilating in anything less than three to five generations, just based on my own family and others I've observed.
While we are on assimilation, we can link back in communal assumptions, and look at the consequence of importing low-trust cultures with preferential selection of their own. Suddenly the indian dominance of the hotel industry, or the story told in Eric's comments about an ethnic dominance of donut shops is a bit less fluffy and feelgood.
You let in feminists, or anyone who cares more about getting fellow women, chinese, jews, indians, pick your identity group, than people who can do the job, and things go to shit. At least if you like things the way the west has basically been doing it.
Coming back to tangents from communal assumptions, libertarianism does not have a good defense against the tyranny of the minority, or even, as Bradford Walker pointed out, psychopaths. The only stop to a tyranny of the minority, or those who would violate community standards, is a stronger set of standards shared and enforced by the same community. Something I believe Eric values, but arguably a significant number of people in the libertarian camp do not.
While we're at it, let's address that it's "just the illegals," and not the number and type of immigrants, whether a society has a right to defend itself and its culture, and how many, over the scope of generations, is too many. I dearly suspect this number is more than zero, but far lower than many of the civic nationalist stripe would be comfortable with.
If I passed a law tomorrow saying that anyone is welcome to arrive, and entry grants right of residence and, down the road, citizenship, no matter what, would that make it right and good? Would those people already entering illegally suddenly be better for us because of the change in laws? Would the culture that gets imported be better for them, or more of the same?
It's legal, right?
Insofar as "people in India are willing to work for less" - I'm far from the only person with offshoring horror stories to tell. Even if they did great work - why are we competing against people with less education, broken credentialist systems that don't teach, don't have a culture of delivering results as promised, don't treat their workers as well outside of pay, or don't care or have to meet the same environmental and safety standards?
One aspect that people ignore is that large businesses are also power centers. They have the money to buy the laws they want - as satirized in the Babylon Bee: Congress Members To Wear Barcodes So Lobbyists Can Scan Prices, Self-Checkout - hat tip to Peter Grant. Given they have their own security, data systems, and span the globe, the large companies certainly have power on the level of smaller governments, and significant influence and independence. Corporate charters grant the leaders a large degree of immunity from consequence, and thus reduces their skin in the game while socializing the costs.
They also don't think long term enough. By this I don't mean the usual criticism that they only look at the next quarter or year, but that even the companies that work to keep their options open four or five years out don't think in terms of generations. And the multinationals certainly have less reason to make their choices of who they do business with, buy from, sell to, with an eye towards the long term good of the culture they sprang from if they are not rooted in that culture, or if doing so conflicts with the bottom line.
It's hard enough to convince a business sometimes that effectiveness and antifragility is far more important than efficiency and the bottom line, and that's just dealing with quarterly or next year thinking.
One last note - the media lies too.
Yeah, we know, so why mention it?
Because there is no damn reason to make a fool of oneself on camera as recently happened with Antifa and Mr. Ngo. Stop fucking LARPing.
Ever had to deal with a bully in school who knew the no fighting rule and was an expert at pushing you out of line or otherwise harassing you in such a way that when the teacher noticed the commotion she only saw you pushing back? Sure, you may win in court if you go in with security and cameras streaming/rolling, and respond proportionately, and make sure to be backing off so that you can't be construed as aggressively seeking a fight - but to the public you'll be shown to be a violent racist thug, just like they edit video of Trump and others to report the opposite of what happened when you see the full clip.
Worse, if you get your face pasted in, you also look like a loser.
There are times those opposed to the petty tyrants that be need to be visible, and public, but unless you have a plan to keep the moral high ground, the legal high ground, and not lose, in the face of a media that will do their worst to make you look bad, you're a fucking moron.
Pick your battles. Don't give them attention to feed off of. Kindof like Razorfist mentioned with Ms. Cortez.