On the same day 27 women and children were massacred in Newtown, Conn., a man stabbed 22 children at a school in China. The Chinese children all survived.

So much for the infamous National Rifle Association claim that “Guns don’t kill, people do.” Obviously, a wacko with a semiautomatic rifle is a far more effective killing machine than someone with a knife.

But the Chinese tale contains another important message. Beijing government media gave massive coverage to the Newtown murders while blocking all reporting of the school attack in Henan province. This was in keeping with Chinese government policy, which tries to hide details of all such disasters.

This time, however, Chinese social media denounced their government’s blind eye toward Henan, as compared with the intense U.S. focus on the Sandy Hook school killings. As the Chinese bloggers noted, Americans know every detail when there is a massacre – of children or adults.

Indeed, we know the detailed bios and photos of each of Newtown’s victims. We also know about Congress’ failure in 2004 to extend a ban of the kind of automatic weapon that killed these first-graders. Given what we know – about this and a string of mass-shooting murders in the last five years – we have no excuses if we fail to take action, this time, on gun reforms.

We know that the gun debate is not about the Second Amendment, which protects the right of individuals to bear arms. Ordinary people don’t need military-grade weapons like the AR-15 Bushmaster used by the Newtown killer. As Sen. Joe Manchin, D-W.Va., a strong supporter of gun rights, put it: “I don’t know anyone in the sporting or hunting arena that goes out with an assault rifle.”

We know that the reduction of gun restrictions across the country has veered into the absurd, and that it has become entwined with Republican political identity. The Republican-held legislature in Ohio, which last year made it legal to carry firearms into bars, passed a bill last week to permit guns in cars in the Statehouse garage. Has partisanship grown so sharp that Ohio Republicans think they need armed protection against Democrats in the halls of power?

Meantime, the day before the Newtown shootings, the Republican-held Michigan Legislature passed a bill permitting people to carry concealed weapons into schools and churches. Only after the Sandy Hook massacre did Republican Gov. Rick Snyder decide to veto the measure. Do Michigan residents really need to pack heat when they attend Christmas services? Do Michigan legislators really think the way to protect children is for teachers to play John Wayne?

We know that America’s obsession with guns is unique in the world. With 270 million privately held firearms – an average of roughly nine guns for every 10 Americans – we have the highest gun ownership per capita in the world by far.

According to statistics of the Organization for Economic Cooperation and Development, Americans have nearly twice as many guns per person as Yemen (No. 2) and 2 1/2 times as many as Iraq (No. 5). Yes, Yemen and Iraq, countries torn by tribal and sectarian violence, where families need guns for their very survival – and where affiliates of al-Qaida still have a foothold.

We know that it is possible in America to change ingrained cultural habits when the public comes to believe those habits are harmful. Who imagined, decades ago, that smokers would become so isolated? That drunken drivers would be punished?

The Sandy Hook massacre could mark the moment when Americans come to regard assault weapons and large-capacity magazines with fear and loathing. That happened in rough-and-ready Australia, after the 1996 Port Arthur massacre, when one shooter slaughtered 35 tourists with semiautomatic weapons. Shortly afterward, the Australian government banned most semiautomatic rifles and bought back hundreds of thousands of others.

We know that no lobbying group, even the NRA, is impervious to pressure. Already, some gun enthusiasts in Congress are rethinking their support for any and all weapons. If the NRA wants to target these legislators, every concerned parent, along with rich gun-control supporters like New York Mayor Michael Bloomberg, should make clear they will offset such efforts. Perhaps the parents of some Sandy Hook victims will join that campaign.

We know there is no one measure that will curb the horrific gun violence in America. But we also know that, if the deaths of 20 little kids and their teachers are to mean anything, this is the moment for action, by rational citizens and by the White House.

Unlike in China, we know what’s happening, and we have a system that lets us bring about change.