Rumours spread by two different but overlapping processes: popular confirmation and in-group momentum. The first occurs because each of us tends to rely on what others think and do. Once a certain number of people appear to believe a rumour, others will believe it too, unless they have good reason to think it is false. Most rumours involve topics on which people lack direct or personal knowledge, and so most of us often simply trust the crowd. As more people accept the crowd view, the crowd grows larger, creating a real risk that large groups of people will believe rumours even though they are completely false.
In-group momentum refers to the fact that when like-minded people get together, they often end up believing a more extreme version of what they thought before. Suppose that members of a certain group are inclined to accept a rumour about, say, the evil intentions of a certain nation. In all likelihood, they will become more committed to that rumour after they have spoken to each other. Indeed, they may move from being tentative believers to being absolutely certain, even though their only new evidence is what other members of the group believe. Consider the role of the internet here: when people see many tweets or posts from like-minded people, they are strongly inclined to accept a rumour as true.
What can be done to reduce the risk that these two processes will lead us to accept false rumours? The most obvious answer, and the standard one, involves the system of free expression: people should be exposed to balanced information and to corrections from those who know the truth. Freedom usually works, but in some contexts it is an incomplete remedy. People do not process information in a neutral way, and emotions often get in the way of truth. People take in new information in a very uneven way, and those who have accepted false rumours do not easily give up their beliefs, especially when there are strong emotional commitments involved. It can be extremely hard to change what people think, even by presenting them with facts.
出典：On Rumors: How Falsehoods Spread, Why We Believe Them, What Can Be Done, by Cass R. Sunstein, 2009
解答者の性格の出そうな問題です。末尾を本文通り「情報の受け止め方は感情的なものであり人々の考えを正すことは難しい」とするか、「表現の自由やバランスの取れた情報と、事実に基く訂正により噂の拡散を防ぐことができる」に持ってくるかで、解答が分かれるところかと思います。実際には本文がネガティブな意見にまとまっているので、「難しい」を末尾に持ってくるのが自然に感じられますが、出典の書籍では「誤った噂が拡がるリスクを減らすために何ができるか」がテーマなので、後者のタイプの要約でもあながち頓珍漢とは言えない気がします（ただ、“it is an incomplete remedy“ とあるので、試験では素直にまとめるのが無難です）。