Interesting article on Free Speech and Guns. It certainly provokes thought.
However, I would like to offer at least some thoughts from the other side.
First, let us recognise that the First and Second Amendments should be at least comparably sacred. It seems clear to me (though it may not be so to others) that we cannot pick and choose from our Constitution; it must stand or fall in its entirety. Similarly, the rights enumerated in the Bill of Rights must be completely accepted or completely rejected - because no amendment is or can be more sacred or more sacrosanct than any other. If we can pick and choose which ones we will accept and defend and which we will relegate to the scrap heap, then no right is sacred any more. The most dangerous concept to come out of the Supreme Court may be 'selective incorporation,' since it does just that.
We have seen the Court repeatedly take a great deal of care to avoid saying just what "[T]he right of the people to keep and bear arms shall not be infringed" means. Effectively, by declining challenges, they have declared it to mean that some, even many infringements are acceptable. Let's turn this around. This is, after all, not a 'fire in a crowded theater' sort of restriction. What if the discussion were not about what consititutes an infringement on the bearing of arms but rather on what constitutes an abridgement of free speech? Or what constitutes compelling someone to be a witness against himself? Or . . . but you get my point. Can we accept that certain specific enumerated rights can be wished away without putting all of them at risk? Personally, I don't think so. As a veteran of the late great hate in Southeast Asia, I have learned not to trust to the benevolence of government, and if we allow those rights to become less than rights, then we are in that respect at the mercy of government.
This does not, of course, answer the question of whether guns secure our rights. I would generally agree with you when you say that violence is shameful. I might disagree about the specific adjective, but certainly violence is deplorable. I don't recommend it - but I recognize that it is sometimes necessary. When I say that I believe that arms in the hands of the citizenry at large guarantees our rights, that is not a glorification of violence; it is merely a recognition of the fact that a free, armed man cannot be enslaved. He can be killed, but the only way he can be enslaved is by first disarming him. As a man is, so is the populace even more.
Similarly, when a citizenry decides to revolt, whether this is justified in the larger view or not, the first necessity is arms.
This leads to your question of when is violence acceptable. I cannot answer for everyone, and in truth, I cannot answer for anyone else. But for me, there are at least some times when I can say that violence is acceptable (though still deplorable). First, when violence is visited upon me or those close to me, I feel it is acceptable to return it in kind, and in such fashion and amount as to assure that the one who has initiated that violence will not do so again, whether from fear of a repeat or from inability. This, by the way, is my own set of circumstances when I would consider it proper to shoot a federal officer. One who identifies himself and endeavors to make a polite arrest, even if that attempt must escalate to violence in response to offered violence, is safe from me. One who begins by offering violence unannounced and unidentified, to my own way of thinking, can properly be shown the error of his ways.
In answer to your next question, no, to me, guns are not an appropriate response to speech alone - ever. Speech which tries to instigate violence, AND which succeeds in instigating that violence, offers an appropriate situation - but that response is not to the speech, but to the violence. Hitler, himself, did little violence and much speaking - but that speaking led to a great deal of violence, which was appropriately responded to with opposing violence. The whole thing was deplorable - but the response was necessary.
I do not see the world as based on violence, particularly violence alone, and I would probably qualify as a gun advocate. I see the world, or at least the advancement of the human species, as based on individual freedom - which means, not the right to initiate violence, but the right and the ability to defend from violence with other, necessary, though deplorable, responsive violence. Slaves and peasants have no such right and precious little such ability.
As our government moves apparently inexorably toward socialism, people look more and more to the government for solutions to problems they perceive. They forget, if indeed they ever knew, that problem-solving is first and foremost their own personal job, and that our government, by the way it was consitituted, can only do what we allow it to do and therefore has no greater power than we do. In seeking governmentally supplied solutions, we allow government to do all sorts of things it was never intended to do, and judging by its track record, government cannot solve one problem without creating several more. The one thing government absolutely cannot do is keep our rights and our freedoms - those are our responsibility and ours alone. We discard even one at our peril.