I wanted to highlight Glenn's argument for why the speech in question should be protected:
This is not an academic question. The right at stake here is absolutely vital. It is crucial to protect and preserve the right to argue that a government has become so tyrannical or dangerous that violence is justified against it. That, after all, was the argument on which the American Founding was based; it is pure political speech; and criminalizing the expression of that idea poses a grave danger to free speech generally and the specific ability to organize against abusive governments. To allow the government to punish citizens -- let alone to kill them -- because their political advocacy is threatening to the government is infinitely more dangerous than whatever ideas are being targeted for punishment, even if that idea is violent jihad.
That sounds a lot like the argument for the right to bear arms. The logic is the same is it not? People need to be able to own and carry guns in order to protect against a gov't that has become so tyrannical or dangerous that violence is justified against it. The founders just got done taking that argument from theory into practical application when they decided to write the Constitution and then the Bill of Rights. Obviously this is something a conservative like Rand Paul would argue. Yet when it comes to speech made by some Muslims or basically anyone who isn't a white guy he is ready to throw people in jail. As Glenn points out, some tea party rallies would qualify as the kind of speech Paul wants to criminalize.
While I think the argument for radical speech and gun rights are the same, I don't think the rights are of equal standing, at least not anymore. I'll grant that at the time of the founding it was probably just as important for the safety of the democratic republic that people be able to own and carry guns as it was that they were able to assemble and speak freely. But the threat the founders faced is largely gone. While they had to rely on militias to defend the country, we have a large and well-equipped military that can defend the country from foreign invaders or domestic insurrections.
The downside to us having such a good military is that it could easily decide to dissolve our democratic republic through a coup and institute a military dictatorship. But would the right of ordinary citizens to bear arms really prevent that? Even the most ardent guns rights advocate doesn't think citizens should have rocket launchers and tanks. So how would a militia fight a modern army? I don't really see a way given the very unlikely scenario in which the US military rebelled. The much more likely scenarios involving the gov't tyrannizing its citizens are the ones Glenn points out, killing a citizen without due process or engaging in warrantless searches. The way to remedy those problems wouldn't be through shooting the culprits. It would be through using speech to call attention to the problem and using democratic devises to enact change and courts to prosecute.
To wrap up, Paul and conservatives have their priorities a bit out of whack. Radical speech is important to all democracies. And it is much less dangerous to innocent people than guns are. And in our modern democracy I'd argue speech is more effective. When was the last time a gun solved a domestic political problem? That's not to say gun rights should be banished. But they should be heavily regulated. And speech should be heavily unregulated.