(who on earth gave it that daft name? Whose freedoms are being protected?)
Bear in mind that the Protection of Freedoms Act is a large piece of legislation, and only one of its schedules relates to parking on private land. Other parts of the act regulate the storage/destruction of fingerprint records by the police and others, the regulation of CCTV use, the protection of property from disproportionate enforcement action, counter-terrorism powers, protecting vulnerable groups, disregarding convictions for outdated crimes like buggery etc., and other measures...
In relation to private parking, the Protection of Freedoms Act also made immobilising vehicles in private car parks an offence. If the case you are currently challenging had happened prior to the introduction of PoFA, the driver may have returned to the car to find a clamp attached, and a private company demanding a fee before they would release it.