The people are reluctant to take that one little step, because they fear being eaten by the others. The symbolic meaning of that little step is a return to humanity. If they would abandon there paranoid thoughts, they may return to normal. Lu Xun wishes that the people would return to their normal behaviors. For example, he said in section 9, "But all they'd have to do is give up that way of thinking, and then they could travel about, work, eat, and sleep in perfect security." Essentially, they prevent each other from being normal.
In section 10, the madman gets upset at the Elder Brother, because he failed to prevent the cannibals from wanting to eat the madman. The Elder Brother also joined the cannibals. The Elder Brother claimed that the cannibals cannot evolve, much like the lizards that the madman mentions. Also, he said that a tenants rent could not be reduced. He explains cannibalism as an early human that failed to evolve into "real humans." In section 8, the madman asks one of the cannibals if eating people was right. I thought this was significant, because the cannibal was unable to answer the question. His efforts to dodge the question made me believe that he knew it was not right. Also, his inability to answer the question suggests that these cannibals are still human, because he seemed upset by the madman. He was very defensive and seemed to be in denial. It was as if he was trying to escape how he had been acting.