Forget for a moment that this is an election year in the United States, and that last week's US Congress hearing on the alleged complicity of American technology giants in human rights abuses in China was as much about grabbing free screen time ahead of the polls as it was an attempt to get at the truth. Democrat Tom Lantos has a point: Google, Microsoft, Cisco Systems and especially Yahoo ought to be ashamed. The hearing was a chance for top executives to explain their positions in China and show they are at least making an effort to protect principles such as freedom of speech in a market where such speech is not tolerated. But Larry, Sergey, Bill, John and Jerry were not on hand. Instead, they sent lawyers, who dutifully stuck to prepared scripts and delivered rigid answers to straightforward questions, further compounding the embarrassment these companies have become. Yahoo general counsel Michael Callahan had to be asked four times whether the company had offered any assistance to the family of Shi Tao, the mainland journalist jailed with the help of information Yahoo had supplied to the government. With much reluctance, he finally admitted that Yahoo had offered none. Microsoft associate general counsel Jack Krumholtz claimed he was not familiar with IBM's well-documented role in the Holocaust, rather than state whether IBM should feel ashamed of helping Nazi Germany by supplying punch-card technology, and by extension, whether US companies ought to feel ashamed of helping the mainland government rein in dissent. Also troubling were the repeated reminders from Mr Callahan that Yahoo no longer owned its business in China. Alibaba.com does. It seems the responsibility - and what we are talking about here is moral responsibility - is no longer in Yahoo's hands. When it comes to responsibility, each in the Gang of Four has taken a similar line - they face a tough choice: comply with Chinese law, or leave. If these are the only options, then perhaps they should consider leaving. Mr Lantos, a Holocaust survivor, is not buying the argument that US companies must comply with mainland law. 'IBM complied with legal orders when they co-operated with Nazi Germany. Those were legal orders under the Nazi German system,' he said last week. True, what China has done is nowhere near the crimes Germany committed during the second world war - 49 cyber-dissidents and 32 journalists jailed versus more than 6 million murdered. But that does not mean we should ignore a wrongdoing when one exists. As a result of Yahoo's actions, at least two men have lost their liberty, while Cisco, Microsoft and Google have held back the forces of liberalisation and freedom by censoring the internet. When the US Congress was debating whether to give the mainland permanent most favoured nation trade status, American companies said their presence in the market would change China. Yet, in the case of the internet companies, China has changed them. Instead of compromising their values, why not simply quit China? It would not be the first time a major US corporation would have put moral responsibility before profit. Look at Leon Sullivan, board member of General Motors, who convinced the carmaker and 100 other firms to withdraw from South Africa after the country refused to budge on apartheid. What are needed are some Sullivan principles for the internet. The US companies have argued that their presence in China has had a 'net' benefit, as though liberty were a positive sum of rights and wrongs. Microsoft points to the 3.5 million Chinese blogs created under its MSN Spaces service. But what good can this service be if words such as democracy and human rights are filtered, or if Microsoft must remove any blog the government claims upsets social stability? The American companies could also argue that quitting China would mean ceding the market to domestic rivals who have no qualms about censoring the Net. US firms worry that mainland companies will grab the spoils - the main worry of the US firms - with no benefit to freedom. Yet, if we apply the Sullivan principles not only to Google, Microsoft, Cisco and Yahoo but also to the foreign venture capitalists who invest in companies such as Baidu.com and NetEase.com, this might deprive mainland firms of one source of funding, and lead them to pressure their government for change. A US Congressman has already introduced a legislative bill that would punish American companies that comply with foreign censorship laws. The draft text includes US-listed firms, which means it will apply to Baidu and its brethren. While one view is these companies will raise capital elsewhere, another view might be these mainland internet firms - deprived of their lofty Nasdaq valuations - will start to see freedom of speech as a competitive advantage. At this point, that bill is just a bill, and it is difficult to say whether internet freedom in China will stay on the political agenda once the mid-term elections pass. But one thing is clear: unless Google, Microsoft, Cisco and Yahoo change their ways, history will not look back on them with any kindness.