There is nothing anarchistic about the legal ways in which the press is protected from prosecution if a source reveals classified materials.
The person who had security clearance and violated it to leak the materials has committed a crime, and sometimes such crimes are committed by people who discover an abhorrent practice and decide that revealing it is worth the price (possible prosecution).
Any organization will have rules that prevent insiders from leaking certain information, but ultimately every employee must be guided by his/her own moral compass. Loyalty to the institution would ideally result in the employee pursuing things internally within the organization first. But in some cases the crimes are so deeply rooted or so broadly ignored that the employee faces the tough decision of whether to blow the whistle or to become complicit in the abhorrent acts.
No legitimate organization would wish to commit abhorrent acts, and so we must recognize such acts as an artifact of bureaucracy and corruption. Thus, like lymphocytes in an organism's immune system, whistle blowers benefit the organization by helping rid it of such toxins.
US law protects the press b/c this phenomenon is understood to effect organizations of all sizes, including governments. Individual whistle blowers are often viewed as heroes because of the personal risks they endure to save their beloved organizations from corruption and malice.
What self-respecting member of the military would countenance such abuses as Bradley Manning learned of when he viewed the war logs when he decided to release them? Loyalty is perhaps a virtue, but it comes below a person's own individual integrity and sense of right and wrong.