Free speech is often hailed among the most significant of our fundamental freedoms. In the Western world in particular, freedom of speech and press has allowed for a range of voices, including voices of dissent that seem to indicate that our democracy is in a sense working. However, free speech is not completely free. There are limits and curbs based on what may be of greater importance in various contexts – such as if the speech might endanger others. That is why we can’t yell “fire” in a theater as a joke – the potential chaos and harm it raises in that context outweighs some one’s freedom to say what they want.
For the record, I’m in favor of the First Amendment guarantee of free speech, with the usual and, I should think, reasonable exceptions (the clichéd but relevant prohibition against yelling “fire” in a school or crowded theater or showing pornography in either venue, for example).