The first and fundamental principal of the first amendment is that content based restrictions on speech are prohibited. The amendment states in pertinent part that "Congress shall make no law....abridging the freedom of speech." Our forefathers felt this language essential to ensuring the existence of a democratic society.
While speech can be restricted based on other factors such as, "fightin words" or "clear and present danger" or threatening manner and the prohibition of obscene speech or expression, hate speech is not prohibited. While repugnant and respulsive this may be, the idea of free expression is fundamental to democracy. J. Holmes coined the term, "the market place of ideas." This term conveys the principal that unrestricted expression allows people to find the truth.
Content-based restictions on speech, aside from obscenity, are prohibited because they pose a dangerous threat to the First Amendment in that inherent in the probition are the essential questions - What is hateful? Who is the judge? If we endow others with the right to decide what is hateful and who can say what, then we are in danger of undermining a democracy.
So while hate speech is awful, and there are ways to restrict it, it is not unconstitutional. As an idealist, I always like to believe that hate speech, because it is so offensive, teaches people how to love, because they don't wish to adopt the beliefs of those who are intolerant of others. "You may call me a dreamer, but I'm not the only one." "Just Imagine" John Lennon.
Though some argue it cannot be protected, there are two main reasons why hate speech should be protected by the First Amendment.
First, it is too hard to differentiate on any objective basis between hate speech and legitimate political speech. Hate speech can be defined as speech that vilifies or belittles a person or people based on such things as their race, their sex, their religion, or their sexual orientation. However, there is much in the way of political speech that is clearly legitimate but which could be seen as hate speech. For example, if someone says that the Bible tells them that God disapproves of homosexuality and that they therefore do not believe that gay couples should have the right to marry, does that not belittle gay people? Such speech clearly portrays gay people as people whose conduct God (and the speaker) dislikes. This can be seen as belittling and vilifying gay people and yet it is surely protected political speech. The lines are too vague between what is hate speech and what is political speech.
Second, we can argue that the best response to hate speech is more speech. When some people engage in hate speech, we must speak out against them, not try to prevent them from speaking. In a democratic society, we deal with speech that we dislike by arguing against it, not by prohibiting it and thereby reducing the amount of freedom in our society.