These arguments are not supported by evidence or history. They are based on misconceptions about homeschooling/unschooling, and a limited frame of reference because most of us went to school and have no experience with alternatives. Unschooling does not mean locking kids up at home, depriving them of friends or opportunities to learn. It means letting children follow their own interests, at their own pace, and allowing them to participate in the larger world rather than getting locked up for 7 or 8 hours a day in a rigid and coercive environment where critical thinking and discovery are actively discouraged. It means supporting and encouraging education tailored for the child rather than forcing them into 12 years of government-mandated curriculum, standardized tests, strict regimentation, surveillance, and an often toxic environment that resembles jail more than living in the real world as productive adults.
These worries strike me as similar to the argument that people can't live moral lives without religion. We know that simply isn't true. I suspect many more people on HN grew up morally without religion than grew up educated and socialized without school, so maybe some of the critics can step back a bit and examine their assumptions, and ignorance of unschooling, before posting the usual objections.