If the ordinary person agrees with the opinion, he could be concerned about his fate when expressing those same views, and would want to stand in solidarity with someone who shares his opinion.
However, even if the ordinary person does not agree with the extreme one, he should be concerned if his freedom of speech is restricted because it sets a precedent. In the United States, citizens have the right of freedom of speech, regardless of whether the opinions they express are popular or not. If this right is taken away from one person, nothing would prevent the government to take it away from others, when they have an unpopular or extreme opinion. Therefore, the normal citizen should care about it as a way to protect his own right to freedom of speech.
