When Lu Xun mentions people's reluctance to "take that one little step", he is referring to their inability to return to a normal state of mind because they are afraid of being 'eaten' by others. This is significant because it shows how easily paranoid and influenced people can become. It is clear that Lu Xun wants people to disregard "that way of thinking" and come to realize that not everyone is out to get you. He emphasizes this point in Section 9 but also notes that people prevent this change from happening by collectively holding each other back through actions and words.
In Section 10 of Diary of a Madman, Elder Brother upsets the madman because he is unable to prevent the cannibals from wanting to eat him. Here, Elder Brother claims that creating change among the cannibals is virtually impossible because they fail (and refuse) to look back and analyze the problems they face. By explaining cannibalism in this way, Lu Xun shows that cannibalism is a peculiar practice that is unable to change and evolve despite being influenced by outside factors. In section 8, the madman inquires if "this business of eating people [is] right". This question is quite significant because of the response it provoked from the cannibal it was directed towards. The cannibal reacts by trying to change the subject of conversation and directly avoid answering the madman's question. It became clear from his response that the cannibal knew he was in the wrong for his actions, but was unable to accept responsibility for them and act accordingly.