It's really a tough job for automakers doing marketing and sales in China, where competition is acute and customers have little loyalty. They have tried a range of gimmicks in recent years.

But there should be a moral bottom line.

Unfortunately, a Buick dealership in the northeastern city of Shenyang used the tragedy of a two-month-old infant to tout its cars last week on Weibo - China's equivalent of Twitter. And Hyundai Motor followed suit.

On March 4, an SUV was stolen with the infant left inside alone in the northeastern city of Changchun. The news spread widely on Weibo after the baby's father called the local police and radio station for help. The next day it was revealed that the infant was choked to death and buried in snow by the carjacker. The online community expressed its deeply felt sympathy and condolences.

The Buick dealership posted a photo of the baby and two of its cars on its official Weibo account to advertise its GPS system that can locate the stolen car.

"A few thoughts on the Changchun stolen car and baby incident: when buying a car it's entirely OK to choose a brand with advanced technology," said the post, which ended with the dealer's sales hotline and online instant messaging accounts.

Though the post was made before tragic fate of the infant was known, the action generated a storm of outrage on Weibo. Some online commentators said it is "marketing at the cost of lives" and "extremely despicable".

Worse was the post on Hyundai's official Weibo account that advertised the anti-theft system on its new SUV Santa Fe, an entry made after the child was known to have died. The action also enraged micro bloggers.

Both posts were soon deleted. The Buick dealership made an apology on Weibo to the family of the victim and the public.

But screenshots saved by users continued to be posted and the negative impact on both brands persists.

The two brands probably didn't expect such a firestorm of fury from the Internet community, but they really made a big mistake sinking below the moral bottom line. They certainly tainted their own brand images.

The Chinese have the same proverb as the English language - a little leak will sink a great ship. It takes decades to build the great ship of a respectable brand but it can take just a moment of negligence to send it floundering.

For those in corporate marketing and PR, at least two lessons should be learned.

First, be careful in the era of social media when one wrong can be easily magnified and have disastrous impacts in just a few clicks.

Second and more importantly, think with both your brain and heart. Never break the moral bonds of respect for human life and sympathy for our fellow man.

Contact the writers through gongzhengzheng@chinadaily.com.cn