The detention at Heathrow on Sunday of the Brazilian David Miranda is the sort of treatment western politicians love to deplore in Putin's Russia or Ahmadinejad's Iran. His "offence" under the 2000 Terrorism Act was apparently to be the partner of a journalist, Glenn Greenwald, who had reported for the Guardian on material released by the American whistleblower, Edward Snowden. We must assume the Americans asked the British government to nab him, shake him down and take his personal effects.

Miranda's phone and laptop were confiscated and he was held incommunicado, without access to friends or lawyer, for the maximum nine hours allowed under law. It is the airport equivalent of smashing into someone's flat, rifling through their drawers and stealing papers and documents. It is simple harassment and intimidation.

Greenwald himself is not known to have committed any offence, unless journalism is now a "terrorist" occupation in the eyes of British and American politicians. As for Miranda, his only offence seems to have been to be part of his family. Harassing the family of those who have upset authority is the most obscene form of state terrorism.

Last month, the British foreign secretary, William Hague, airily excused the apparently illegal hoovering of internet traffic by British and American spies on the grounds that "the innocent have nothing to fear," the motto of police states down the ages. Hague's apologists explained that he was a nice chap really, but that relations with America trumped every libertarian card.

The hysteria of the "war on terror" is now corrupting every area of democratic government. It extends from the arbitrary selection of drone targets to the quasi-torture of suspects, the intrusion on personal data and the harassing of journalists' families. The disregard of statutory oversight – in Britain's case pathetically inadequate – is giving western governments many of the characteristics of the enemies they profess to oppose. How Putin must be rubbing his hands with glee.

The innocent have nothing to fear? They do if they embarrass America and happen to visit British soil. The only land of the free today in this matter is Brazil.