In my opinion, this freedom is the most important. Yet, it will induce the most anger of any other Amendments. It also requires the most tolerance.
Someone (H-Nox, I believe) brought up the burning of our flag. This is a perfect example, because it infuriates me, yet I have to respect the rights of this so-called person.
Of course we have also heard many court cases involving free speech. Check out U.S. v Eichmann (1990). The Supreme court said, Government's interest cannot justify its infringement on First Amendment rights.
This conclusion will not be reassessed in light of Congress' recent recognition
of a purported "national consensus" favoring a prohibition on flag-burning,
since any suggestion that the Government's interest in suppressing speech
becomes more weighty as popular opposition to that speech grows is foreign to
the First Amendment. While flag desecration -- like virulent ethnic and
religious epithets, vulgar repudiations of the draft, and scurrilous caricatures
-- is deeply offensive to many, the Government may not prohibit the expression
of an idea simply because society finds the idea itself offensive or
So, there it is in black and white (Red in this case).
Free speech protects flag burning, hate-speech, and even groups such as NAMBLA are protected to some degree. But, it has to be tolerated. As much as it pains me, you can not suppress somebodies rights, because if you do, you are opening the door for your own rights to be suppressed.
And that my friends, is the hard part of living in a free society.