Good things that arise from collective action, like culture, collaboration, and community, don’t count. And any debt individual triumphs owe to collective stability is conveniently forgotten. 

As I explained, “collective” norms like language and culture and community are necessary and usually good, but are emergent from individual self-determination as opposed to top-down from individuals who are supposed to represent the collective. There is a big difference between collectivism and individually voluntary “collective” action / emergent norms - that is whether the collective or individual is considered primary. The distinguishing feature of collectivism as opposed to individualism is not interaction or cooperation, but the ideological basis of justification for analysis and, in praxis, for proactive physical coercion.

The problem is that while (as I said) collective norms and action do exist and are obviously beneficial (language, culture, law, morality, etc.), they do not come from and cannot be known a priori by individuals, including those who control top-down coercive institutions supposed to represent the collective. It is the myth that they (1) can and (2) will act in the interests of “the collective” that subsidizes such such top-down coercive institutions.

Take something that seems collective. We’ll use the angry lynch mob feeding off its own energy and collective prejudice… the mob violence should properly be attributed to the individualism. 

It should be attributed to whatever motivated the individuals, yes, obviously. The individual is the primary unit of analysis. That does not mean they were motivated “by individualism,” though they could hypothetically be motivated by anything (more likely a collectivist ideology like racism than anything else).

Whakahekeheke concludes that we can never truly know the values and desires of somebody else

No, you seem to have drastically misread. We certainly can know what someone else values. They reveal their values by their voluntary choice (and we can safely assume physiological generalities like the desire for air, water, food, eyesight, etc). However, though I can guess, I can’t know what you value better than you know what you value. 

—so collective actions and collective values are somehow inherently impossible.

Non sequitur. We certainly can cooperate and act collectively and we obviously can have shared values - this is how the world works. What is impossible is for you (or a politician) to know what those values are or actions should beyond individually voluntary human interaction. Again, the point is that you can’t know what some adult values better than they know what they value.

This is going to come as a real shock and disappointment to a lot of philosophers who have been laboring for thousands of years to have all their work dispatched so quickly.

Yes, it did, in 1972 when economist Kenneth Arrow won the Nobel prize for the Arrow Impossibility Theorum  that logically proved collectivism was intellectually worthless bunk - from Rawls to Marx. Arrow was not the first to do this, and it is easily derivable from common sense, but his thorough logical proof cemented microeconomic method (marginalism) in economics, which is what drove Marxian and orthodox Keynesian economics out of academia (also, their predictions failed…). Unfortunately, the undisputable axioms of methodological individualism have not yet spread to the social sciences of sociology, anthro, political science, etc. or even consistently through all schools of economics.

You think you bought that Kei$sha album because you invented your own musical tastes? 

No, now you’re talking about metaphysical free will, which is irrelevant to this issue. Whether your individual values are shaped entirely by your environment, genetics, or whatever - they are your values and I can’t know them better than you.

It means paying attention to relationships. It means community. It means striving to understand others rather than assuming they are all either identical to us or intrinsically unknowable. It means communities attempt to give individuals the support they need to flourish—even when that flourishing means pretending they’re not part of a community.

I’m very much in favor of all that, and none of it needs to be based on or is at all helped by the superstitious notions of collectivism