Being a U.S. citizen gives you the right to voice your opinion, either with words or through your actions. In civil rights law, "speech" refers to all kinds of expression. But the U.S. Constitution, and the way it's been applied by courts, includes some exceptions. Your words and actions may not always be protected, depending on how they affect others.
Obscenity Is Not Protected
Obscenity is an exception to the First Amendment, which protects freedom of speech. If you shout vulgarities from your front porch for the whole neighborhood to hear, the authorities will probably charge you with disrupting the peace, and the First Amendment won't protect you. Your behavior would be offensive to a reasonable person, and it would have no value to society. The obscenity exception gets complicated when applied to the arts, because art benefits society. Whether a work of art is offensive can be a matter of individual taste.
You Must Prove What You Say
The U.S. Constitution doesn't protect your right to freedom of speech if you tell lies about someone. Slander occurs when you say untrue things to others. Libel, by comparison, occurs when you make untrue statements in print or by broadcast. Slander and libel are not protected by the First Amendment. The person you lied about can sue you in state civil court. However, your accuser usually must prove that you acted out of malice (in a deliberate attempt to cause harm), that you did in fact cause harm, and that you have no proof that your statement is true.
You Can't Hurt People or Incite Trouble
In 1942, the U.S. Supreme Court added "incitement" to the list of things not covered by freedom of speech. "Fighting words" are against the law and not protected. You can't abuse someone verbally, or use words to rile a crowd into doing something illegal. Law enforcement can criminally charge you for your conduct, and you wouldn't be able to claim that you were exercising your constitutional rights.
Sometimes the Lines Blur
Behavior aimed at a general group is protected by the First Amendment. You can declare a dislike for a whole race of people, or for everyone of a certain religion or sexual preference, and you'd be within your rights. But there's a fine line that you can't cross. If what you've said causes someone else to act out against these people or hurt them, you've incited them. If you make hateful comments to someone else, one on one, based on that person's religion, sex or race, these are fighting words and not protected.
A Civil Rights Lawyer Can Help
The law surrounding a U.S. citizen's right to freedom of speech is complicated. Plus, the facts of each case are unique. This article provides a brief, general introduction to the topic. For more detailed, specific information, please contact a civil rights lawyer.