For a main point question we need to figure out why the author wrote this passage. I think that the end of the first paragraph is probably the best summation of the entire passage and the authors reason for writing it: some critics of philosophical anarchism attack the viewpoint on account of its supposed moral consequences, but those critics are mistaken since anarchism does not actually entail those consequences.
The rest of the passage is the authors defense of anarchism against the arguments of these critics, and showing that anarchism is actually compatible with moral duties. In other words, the passage is the authors defense of anarchism against critics who claim it eliminates moral duties.
