Give me the liberty to know, to utter, and to argue freely according to conscience, above all liberties ~ John Milton
Free speech is the foundation of all other freedoms. There can be no defence of any other rights without the right to express yourself according to your conscience. Anyone who does not understand this does not understand the nature of rights, because true rights are intrinsic to our nature as human beings and can only be defended through the free expression and actions of individuals. Only those who believe that rights are privileges granted by authoritarian leaders could believe that free speech isn't a prerequisite for their preservation.
Oliver Wendell Holmes said that the protection of free speech contained in the First Amendment to the US Constitution was not 'for those who agree with us but...for [those] we hate.' This is self-evident - the right to say something that everyone agrees with doesn't need protecting, it is only the things other people find offensive that do. In other words, the right to free speech is the right to express hate speech.
It astounds me that so many people today appear willing to give up the right to free speech. A free speech rally in Boston on Saturday drew a small handful of supporters and 15,000 counter-protestors, which led to the police to close down the rally. Leaving aside the newspaper reports that the pro-free-speech people were 'right-wing' (as if that is offensive in itself), I think it is amazing that 15,000 people in the land of the First Amendment would assemble to counter-protest against free speech.
The irony is that if the counter-protestors achieved their aim, they wouldn't have the right to express their views. This exposes the peril of going down a path of abrogating free speech - if we lose that right, there is no easy way back. How do you advocate for something you don't have the right to advocate for?
If you can't express your views, the only option left to make your point is violence, but I suspect the counter-protestors know that and it is precisely what they want to bring about.