The National Security Agency has been criticized for decades due to the very nature of its purpose; no one likes the idea that someone can read their emails, listen to their phone calls, or act as an observant third-party on any private two-way communication. But, at the end of the day, so long as the government in and of itself is not a bad actor, the NSA's sole purpose is to facilitate the protection of the citizenry.
Enter the Data Encryption Standard, a new cipher for the computer age and employed up to 16 enciphering keys to encode blocks of text, designed as a joint venture between IBM and the NSA. While simple enough on the surface, the technique created billions upon billions of possible permutations, so many that the even the most state-of-the-art computers of the time would have trouble cracking it. So what's the problem? Wouldn't it be a good thing that after so many years, civilians finally had access to perfect privacy? Well, not if its the height of the Cold War; not if Russian agents could use that very same ultra-secure network to plot attacks or demonstrations to undermine western democracy.
The NSA, vigil as ever, took notice of this inherent risk of the system, and handicapped the DES, leaving it susceptible to brute force attack from their machines, but relatively impervious to commercially available computers. This way, the NSA could still intercept messages sent over private networks, monitoring their content while still allowing a degree of security from unwanted prying eyes. In this sense, the NSA's decision to handicap the DES was justified, as their reasoning to do so was in line with their cardinal purpose: facilitate the safety and security of the citizenry. In allowing the DES to remain too complicated for commercial computers to crack, the NSA even allowed for the enhancement of civilian privacy while not contradicting their inherent purpose. To this end, the NSA was justified in their actions, as their building in a weakness was not to completely destroy the concept of digital purpose, but rather to better enable their ability to intercept and act on potentially malicious communications; their decision was ultimately for the greater good.