I've recently read a Newseek article about that issue. What do you think about it?
It is one of the glaring inconsistencies in American Jurisprudence, there aren't really that many, but this is definitely one. The constitution is absolutist, it says that 'Congress shall make no law...abridging the freedom of speech, or of the press'...none, whatsoever, no law against inciting violence, no law against personal threats, no law against child pornography, no law, period. This worked just fine until the 14th Amendment was ratified and the Incorporation doctrine passed into law; before then, you could just go to the State Legislature to abridge the various freedoms you happen to not like. But after the 14th Amendment, this restriction applied to the states as well as the federal government. The governments should have just gotten out of the business of speech and obscenity, but for cultural reasons that are slowly disappearing they didn't. This lead to several clearly artificial categories of speech and a hierarchy of those categories to balance with a hierarchy of competing government 'interests'. These categories would seem totally arbitrary at first glance if not understood within the context of American culture; the revolution taught us that violence is good and noble, but we have not had a similar cultural event to infuse the idea that sex and obscenity are also good and noble and add to that our impoverished cultural inheritance from the puritans...they're arbitrary categories defined by historical accidents.
As a result we have some very weird situations where the intent of speech is judged, back in 2004 a woman was arrested for removing her top in protest of laws that treat male nudity different from female nudity, the arrest was ruled unconstitutional since it was a political protest and political speech trumps all other categories of speech and trumps nearly all government interests, no matter how 'compelling'. Several other women arrested the same night for the same offence were convicted and fined because their actions were ruled to not be politically motivated.
It's a real problem with the system that will hopefully be corrected in the coming decades, I still think our system better protects liberty than most (with the possible exception of the draconian penalties imposed for speech classified as 'child pornography' by the courts...but I don't know enough about how other systems deal with this issue to compare), but this is certainly a fair point of criticism.