The point I always trip up on in coming to agreement with anarchist thinking (to which I'm generally very aligned) is when it comes to non-proliferation of dangerous technologies (for want of a better phrase), of which protecting the environment is the most obvious example. It's where older texts feel most outdated, in lacking that modern context, and so far I already get that vibe here (especially skipping to the end to see his rebuttal of perceived arguments against). Some regulation of free association is required to tackle issues such as climate change. Less obviously but similarly there needs to be ethical debate as a society at large that can then also be enforced universally when it comes to things like genetic engineering. Something typically state-like is needed to ensure a handful of people don't create a virus that takes out the population, for example. Or to ensure that a nuclear power plant is built to strict and exacting safety standards. Enforcement of standards in general is something I can't consolidate with my perception of an anarchist society. The modern state attempts to free its citizens from the impossible burden of assessing the danger of all undertakings, be it in food standards or building codes, not just for the direct recipient but for bystanders who may be adversely affected regardless. The state cannot be wholly dismantled without adverse affect in those areas.
That's a bit stream of consciousness-y, because I can't quite coalesce those objections down into a single summarising point. It's something like "there are some things we really all need to agree on, and rely on being upheld".