I think that Thoreau's significance in this quote is to stress the idea that human beings should resist conformity in as many ways as possible. For Thoreau, when individuals succumb to conformity and homogeneity in thought without threat or compulsion from a higher authority, this becomes a very sad statement in what it means to be a human being. The idea of what an individual is meant to be is one that is not synonymous with the idea of social conformity. Later on in the passage, Thoreau speaks of how the acorn and the chestnut exist side by side, but live their lives in accordance to what is embedded in their nature. One does not seek to dominate the other or repress the other. This is where he sees human identity as existing. For Thoreau, the need to reflect one's own sense of individuality is essential. This is something that he believes in its most sincere manner. In Thoreau's logic and understanding, what it means to be a human is to not capitulate to what others wish or want simply to be accepted. This is critical in Thoreau's argument in Civil Disobedience because it strives to embrace the very nature of what human beings are and how they should act.