The terrorist attacks in France have precipitated an unprecedented show of solidarity against terrorism as more than a million people, including 40 world leaders, marched through the streets of Paris. They even brought together Israel's Prime Minister Benjamin Netanyahu and Mahmoud Abbas, president of the Palestinian Authority. This may be what The New York Times columnist David Brooks calls a "teachable moment", when people's attention is focused on a tragedy and their minds are open to ways to prevent a recurrence. It is natural that people around the world have sported the slogan "Je suis Charlie" - I am Charlie - but, in truth, very few would want to be identified with the deliberate attempt to be provocative and to mock other people's beliefs that marked the history of the Charlie Hebdo magazine. In fact, Charlie Hebdo arrived on the scene after another publication, Hara-Kiri , was banned by the French government for making fun of the death of former French president Charles de Gaulle. The massacre at Charlie Hebdo is a reminder that, for responsible journalists, there are limits to rights, including freedom of expression, when other people's rights come into play. It is encouraging that, in the aftermath of the Charlie Hebdo massacre, a number of thoughtful pieces have appeared. Brooks, for example, has pointed out that the Charlie Hebdo newspaper "wouldn't have lasted 30 seconds" if its editors had tried to publish it on any American university campus because "student and faculty groups would have accused them of hate speech". Not surprisingly, Chinese commentators have also weighed in on the issue. Xinhua published a commentary saying that while violence related to terrorism should be condemned, "it is high time for the Western world to review the root causes of terrorism, as well as the limitation of press freedom, to avoid more violence in the future". The commentary described what it called one of the most offensive cartoons published in Charlie Hebdo , which showed "the Prophet Mohammed crouched on all fours with his genitals bared". It may be going too far to say that abuse of free speech is a "root cause" of terrorism, but there is little doubt that it is capable of triggering violent protests around the world, as occurred a decade ago when a Danish newspaper published cartoons of the prophet. Feisal Mohamed, a Canadian-born professor of 17th-century English literature at the University of Illinois, was quoted as saying: "Ultimately, the perpetrators of violence are responsible for the violence. But this does remind us that free speech is always a balancing act, and one should take the likely consequences into consideration." That, of course, is also true of responsible journalism. Religion is a highly sensitive topic. A cartoon that mocks deeply held religious beliefs is like waving a red flag at a bull. Unfortunately, when the bull charges, those trampled won't be limited to the handful of flag wavers. Frank Ching is a Hong Kong-based writer and commentator. frank.ching@gmail.com . Follow him on Twitter: @FrankChing1