However, it is not a shield behind which individuals or groups can hide to silence other's speech. This is precisely what the protesters did. They made noise to prevent Bachmann from voicing her perspectives and robbed her of the right to speak. This is the same tyranny that occurs when a speaker (or protester) is thrown in jail or punished in order to be silenced.
Free speech is not about words or sounds which emanate from one's mouth. It is about prohibiting coercive force from being used to silence one's ideas; regardless of how smart, crackpot, or weird these ideas are and certainly regardless of whether one agrees or disagrees with them. The coercive use of the weapon of language to prohibit another from speaking is as tyrannous as using any other coercive method to silence different opinions.
It does not matter who one is, whether a Tea Partier shouting down a Democrat or an OWSer shouting down a Republican, these techniques are abhorrent. They are a direct affront to and violation of free speech, despite trying to hide behind the banner of this right. Free speech is needed to preserve the dialogue that underpins democracy. If we allow anyone to silence others, we will destroy the fabric of our system.