Here is what the US Constitution has to say about freedom of speech.
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
Let's parse that.
The first word -- the subject -- is Congress. The document is speaking specifically about the United States Congress, an elected legislative body.
The next four words are "shall make no law". The subject, Congress, is prohibited from making some kind or other of law.
The remainder tells us just what sorts of laws the subject may not make. Among other things, the prohibited class of laws includes laws that abridge free speech.
The first amendment, like most of the first ten, is a constraint upon the actions of the US government. They're kind of analogous to the Ten Commandments: "thou shalt nots" for the US government.
I'm not so constrained, because I'm not the US Congress. If you are hanging out at my house and you start talking about how "defectives" like me belong in gas chambers, I will ask you to leave, and I won't be polite about it. Your freedom of speech has been abridged, and I am well within my rights to do so. On the other hand, you are legally permitted to go out on the street corner here in the United States and shout that kind of vile filth with a megaphone.
However, keep in mind that freedom of speech does not mean freedom from consequences. By yelling on the street corner, you have let everyone know that you hold some really distasteful views. They are well within their right to shun you. It's an ancient practice. Shunning by private citizens isn't constrained by the US Constitution, and in fact, I'd argue that it is a form of free expression.
As far as I can tell, the position held by so-called free speech absolutists or free speech extremists is as follows. I should be able to say whatever I want, wherever I want, whenever I want, without fear of consequences. This is a far cry from what the US Constitution says about free speech.