I am following some interesting threads at the moment on this very topic. The discussion is at times heated and personal. It is rarely focused on the legal issues except in abstract ways and generalizations. The discussion is multi-jurisdictional and therefore comparative in nature.
Although the topic in a more general sense is the freedom of speech, the heart of the issue seems to be more focused on defamation, slander, and libel.
I tend to believe that the Internet has developed very much as an anything goes forum. The law is lagging behind and it does so as old style media laws are trying to be remodelled to fit new style media. Defamation gets tricky in this scenario. For example, does defamation occur at the point of upload or download when we are talking about electronic publishing? How much liability can be attributed to webmasters or bloggers that do not censor third party material? How anonymous are anonymous bloggers?
In terms of anonymous bloggers. This is an old debate and one that cyclically, at least, raises its head every now and then. Most of you reading this will know that I am not an anonymous blogger. The ugly mugshot you see in my profile is indeed me. Anonymous bloggers would also include those using pen names. I am for anonymous bloggers. My point on anonymous blogging relates to how anonymous you really are. I have learned that you can be truly anonymous if you are familiar with the technology and know what you're doing. For the rest of us not so techno-gadgety (amateurs) blogging using a pen name or just the title anonymous is probably not affording you the degree of anonymity that you think.
But back to freedom of speech. Are the questioning of people's sex lives or their preferences, whether it be sexual or political, or making disparaging remarks about specific individuals know or anonymous, or the threatening of physical violence off limits? Do people have a right to be offended?
I generally believe the trading of insults is an attempt to mark deficiencies in sound sustainable arguments. The insults are simply detracting from the arguments. Nevertheless, to each their own. However, when you start writing about particular people on your blog then I consider this to be an open invitation to the other party to comment. If the post is personal and disparaging of the other then I think you have an obligation to allow the targeted person to comment.
Defamation normally occurs where what is said is untrue, factually inaccurate. Does defamation occur on the Internet? Yes, there is case law to say that it does. In terms of precedent and interpretation of the prevailing laws this is still a much more fluid situation.
With great power comes great responsibility. The Internet provides us, the regular people, with a vast and wide forum. We have an obligation to exercise a degree of caution when wielding this power. After all, I am sure that I read somewhere that "the pen is mightier than the sword!"
Have a good weekend!