Why is the US sending some of its best young minds to jail? On Friday Jeremy Hammond, a 28-year-old digital activist from Chicago, will learn how many years he is to serve for participating in the 2011 hack of the private security firm Stratfor. "I believe in the power of the truth," said Hammond, pleading guilty to helping liberate millions of emails from the company, which is paid by large corporations to spy on activists around the world. "I did this because I believe people have a right to know what governments and corporations are doing behind closed doors. I did what I believe is right."

Like the others who took part in the Stratfor hack, Hammond wasn't out for money, and he didn't get any. Nonetheless, he has spent the past 18 months in prison, including extended periods in solitary confinement, and now faces a 10-year prison sentence. Hammond is the latest target of a global witchhunt against hackers, whistleblowers and anyone who seeks to release private information in the public interest.

The witchhunt is being led by the US government, but its targets are international: Lauri Love, an activist from Suffolk, was arrested in Britain last month and may face extradition on charges of hacking into US government networks and a possible decade in a US jail. The legislation used to single out and lock up these people is the Computer Fraud and Abuse Act, a flexible law that allows US courts to impose almost indefinite sentences against any crime committed with a computer, down to simple violation of terms of service.

In practice, by some staggering coincidence, the digital crimes that get prosecuted are those that happen to make governments and large corporations look foolish. Financial damage is the main thrust of the prosecutors' claim against Hammond and his fellow LulzSec members, but it isn't really the money that matters. Hammond is being asked to pay back just $250,000; by comparison, you would have to embezzle tens of millions of dollars to get an equivalent sentence for corporate fraud in the same Manhattan courtroom.

No, what matters is that people are using their computer skills to expose uncomfortable truths – including Stratfor's alleged involvement in spying on the Occupy Wall Street protests. "Punishment has to be proportionate to the harm caused," said Hanni Fakhoury, staff lawyer at the Electronic Frontier Foundation. "These punishments are excessive."

With the right skills, you no longer have to hide out in a lonely Washington carpark to leak classified information. You don't have to break into a building to steal documents that might be in the public interest. You don't even have to put your trousers on. All you need to do is sit at your computer and type. The practical risks of hanging out the mucky bedsheets of power are decreasing just as a generation that has grown up with a weary distaste for government lies hits adulthood. Clearly, something has to be done to make them fearful again – and fast.

The witchhunt against hackers and leakers is designed as a deterrent. That, after all, is the logic behind sending people to prison: threaten potential scallywags with the loss of their freedom and livelihood and they might just fall in line. The wildly disproportionate sentencing of young digital activists suggests that there's something the US government and associated nation states are anxious to deter. The trouble is that this deterrent looks rather likely to backfire.

If one thing unites the hackers and whistleblowers hunted by the US government over the past three years, from Chelsea Manning and Edward Snowden to notorious prankster Andrew "weev" Auernheimer, it is that they have little respect for the moral authority of the US government and its mechanisms. They are in their teens and 20s; they grew up in the Bush, Blair and Brown years and came of age just as the financial crash of 2008 swept away the socioeconomic justification for Anglo-American imperialism. The online culture that they helped create believes deeply in transparency and, to that culture, digital activists who risk everything for the public's "right to know" are heroes.

Jeremy Hammond is not the first information activist to be made a martyr by the US state, and he is unlikely to be the last. There are a lot of things you can do, if you are the most powerful nation on Earth, to make individuals afraid. You can destroy their chance of a safe and happy future. You can lock them up for years. But the one thing you can't do, ever, is force them to respect you – and if you can't do that, on a basic level, you have already lost.