This is a write up of facts about freedom of speech, draped loosely around the overly simplistic thesis that freedom of speech = good. I generally agree with your main points, and I still found the essay unconvincing. I have to imagine that someone who disagrees with you would react much more negatively.
Freedom of expression
Why not start by defining this right off the bat? Really, how can you defend something without first deciding what it means? You mention that freedom of expression has limits at the end of the essay, but of course, if you put limits on something, it is no longer really free. You might frame your defense of freedom of speech as a valuable liberty, bearing in mind that liberty and freedom are not synonymous. You could then look at how the responsibilities inherent in the concept of liberty imply certain restrictions on speech, but that beyond those restrictions, it should be free. So, making your views available to the public is a right. Forcing other people to listen to them, by say yelling through a bullhorn at 3:00am in front of a hospital, is not. However, this restriction is "content-neutral," in as much as it applies to everyone. You are also not allowed to use speech in ways that would cause public or private harm. So, no yelling "fire" in a crowded theater unless there is actually a fire. No accusing a doctor of being incompetent without proof (libel and slander laws)either.
You might then look at how most debates over free speech are really debates on over where to draw the line between valid public discourse and harmful speech. Hate speech, for instance, often includes material that explicitly calls for violence against certain groups of people. Should it be banned? What about hate speech that denigrates certain groups of people based on race or religion, but that does not explicitly call for violence? Does such speech nonetheless create an atmosphere of violence, in which violence is more likely to occur? But doesn't this line of questioning lead to a slippery slope in which anything that could cause dissension or offense can be banned lest the debate spark violent reactions? And is it not the case that the law holds each person responsible for his or her own actions? So, though speech be meant to incite violence, or even merely create an atmosphere conducive to it, yet it is not the same as an act of violence, and the expression of it should not therefore be a crime. If someone commit an act of violence as a result of speech, then let that person be punished. And so on. All of which leads to the question of where the line should be drawn, and what principles should be used to determine this.
Put another way, it's much like the debate over gun control, which really could be called the debate over weapon control. Clearly, nuclear weapons, biological and chemical agents, and the like, should not be available to anyone who wants them. Just as clearly, banning knives would be stupid. Guns fall somewhere in the middle. They are powerful enough to be very dangerous, and have little use beyond killing. However, a reasonable case can be made that an armed populace is the best defense against the possibility of tyranny, and that guns are common enough among the criminal element that they are necessary for those truly interested in self-defense. Some forms of speech clearly deserve to be banned, as mentioned above. Banning other forms of speech is clearly tyrannical. But its the stuff in-between that causes all the fuss.
Finally, your examples, while very topical, seem to have been chosen at random. If you want a topical example that is more on topic, look at the debate over the anti-Obama protests that have been taking place. Here are some links:
nytimes.com/2009/09/30/opinion/30friedman.html?_r=1&scp=8&sq =Obama&st=Search
news.yahoo.com/s/uc/20090930/cm_uc_crbbox/op_2311458
The first one advocates throwing someone in jail for putting an opinion poll on facebook. Not some nutcase, either, but a venerable New York Times columnist, who is in fact cheering on an actual Secret Service investigation. The second one points out that the left doesn't seem to mind overlooking violent speech, and even violent acts, when the protesters are on their side.
Also, read John Stuart Mill. utilitarianism.com/ol/two.html
His defense of freedom of speech is excellent, and worth reading and citing.
Sorry, this post is getting a bit long. Hope some of this helps you.