The First Amendment does not protect all forms of speech and expression. For instance, it is illegal to shout "Fire" in a crowded room. It is illegal to incite crowds to violence. Obscenity can be regulated. You are still responsible for the consequences of what you say. If you say things that are untrue that cause damage to another person, you are responsible for that. Libel and slander require that the person with the complaint demonstrate that the information is false, that the person knew the information was false when they spread it, and that it caused damage to the person's business, reputation, etc.

The First Amendment protects one against most government action that would infringe upon the right to free speech. It does not provide blanket protection from having to pay for the consequences of that speech. In that same sense, the 2nd Amendment's protection of the right to bear arms does not act as a shield against liability for shooting someone.

Libel and slander are not protected speech, and they are pretty clearly defined by law in most cases. Basically, yes you have a Constitutional right to free speech, but your rights end where another citizen's rights to privacy, safety, or liberty begin.

To add to (or rather refine) what has been said already... the 1st Amendment is a restriction on the legislative power of Congress ONLY. Hence the opening words, "CONGRESS shall make no law ..." The rights defined in the Bill of Rights are NOT a testimony to the birthright of every human being, or even every American, but are actually "negative rights", which is to say a list of wrongs for the Federal government. The restrictions the Bill of Rights imposes upon the Federal government do not apply to any private person or other entity or institution outside the Federal government (and, after the 14th Amendment, the State governments). That's why your boss can fire you for calling him a fathead, high schools can censor student news papers, and colleges can implement outrageously totalitarian speach codes. Slander and Libel are crimes long recognized by Common Law which is antecedant and foundational to the Constitution. No legislation or regulation is necessary to make slander and libel illegal/criminal and actionable. The 1st Amendment Freedoms of Speech and the Press are really nothing more than the freedom to openly discuss and criticize the Federal government, its policies, its officials, and those seeking Federal office. Still, if you slander or libel (knowingly lie about someone with the intent to defame them) an official or a candidate, and it costs him his post/election, or damages him in some other concrete way, he can bring both civil and criminal charges against you personally.

A long time ago you asked a question about unjustly flagging a question involving the word "fortnight." What ever happened? Libel & slander are very difficult to prove in the US> In England it is much easier. The American problem seems to resolve around whether the alleged slanderer has knowledge that his remark is untrue and if he actually desired to hurt you with the slander or libel, and lastly, whether there was any actual loss due to the slander or libel.

To win a defamation case you need to demonstrate that someone said things about you that are not true and damaging to your reputation. Free speach does not include lying in order to inflict damage on someone. That kind of damage can have a serious negative effect on one's ability to earn a living and create substantial hardship that goes well beyond simply being embarrassed. The ability to feed one's family is a very important right that absolutely deserves the protection of the law.