Freedom of expression, I'm all for it. Except, of course, when it comes to my teenage son, who is banned from Facebook for being a bit too free with his expressions.

Yes, I'm like China when it comes to Facebook, but it's for his own good. With freedom comes responsibility (Eleanor Roosevelt may have said that, too), and it's clear he can't handle it yet.

Free speech was the subject of loud and sometimes rude discussion at dinner with friends over the weekend. How far should it go? Where do we draw the line? Does free speech mean you can say anything, to anyone, anywhere? The problem wasn't that we didn't agree - and we didn't - it was that we all wanted to exercise our right at the same time. In the end, we had to take turns and try to listen to each other, which wasn't easy.

Columnists understand perhaps better than most the value of free speech and the responsibility that goes with it.

I exercise the right to freely express myself every time I sit down to write this column. I can say what I want, how I want. It's my viewpoint, my column, my call.

Readers are welcome to disagree and many do. That's free speech.

But freedom comes with limits and responsibilities; the right to free speech has never been absolute. I don't have a right to defame, for example. As Oliver Wendell Holmes once said, "The right to swing my fist ends where the other man's nose begins."

How far do I go? Should I go there at all? Every time I exercise my right, I'm making choices. Some things I can't write about because of potential conflicts of interest, some things I won't write about because the hurt caused would outweigh any benefit.

Most columnists would admit to choosing their words carefully; not just because it's better to be understood than not, but because causing offence for the sake of it is counterproductive.

There might be a market for columnists who are deliberately offensive and disrespectful but probably not on this paper.

And I probably shouldn't admit this, but being paid to muse aloud every week has always felt like a privilege. It's my right to say what I want but not my right to have a column.

Free speech, it's often said, is the lifeblood of democracy. The freedom to express our ideas and opinions, to have them tested in "the marketplace of ideas", advances truth, safeguards democratic rights and allows us to develop emotionally and intellectually.

Human beings cannot flourish, nor societies progress if free speech is stifled and suppressed.

Yet not all speech is created equal, and while most people have no problem arguing for the protection of political speech, the line becomes more difficult to define, or defend, when it comes to low-value speech like pornography and obscenity.

Why, for example, should protection be extended to a T-shirt showing a near-naked, masturbating nun captioned "vestal masturbation" on the front and "Jesus is a c***" on the back? If there was any redeeming social commentary or artistic merit there, it was hard to see it for the offensiveness.

The chief censor rightly banned it in 2008 (classifying it R18 would have presented some obvious problems) but the decision wasn't popular with some academics.

In China, the free speech debate is more clear-cut.

The awarding of the Nobel Peace Prize to Chinese dissident Liu Xiaobo is a reminder of what freedom of speech really means.

Liu is serving an 11-year sentence for his role in organising Charter 08, a manifesto for reform signed in 2008 by hundreds of liberal intellectuals and dissidents.

It called on China to recognise "universal values" and join "the mainstream of civilisation [in] setting up a democracy".

Support for the concept of universal values of freedom and democracy is said to have been gaining ground since the earthquake in Sichuan province in 2008 which killed 80,000 people. A liberal newspaper praised the Government's rapid response, saying it had "honoured its commitments to its own people and to the whole world with respect to universal values".

Since then an ideological battle has been simmering. As a recent article in the Economist said, it's not quite true that China is rejecting Western values; rather, it is fighting over them. The fight surfaced last week when a group of 23 retired Communist party elders released a letter calling for an end to censorship in China. In the West,we claim the right to free speech not to challenge our institutions, or to call the powerful to account, but to ridicule, offend and exclude. Talk isn't just free in the West, it's cheap. We don't know when to shut up.

By Tapu Misa