Fingerprint scanners are not yet prevalent in modern smartphones, and fingerprints are one of the primary ways that law enforcement can trace / track individuals. If the NSA, which has already been shown to have backdoors into Apple's systems, was able to access fingerprint data on a massive scale, this would be a massive affront to privacy for millions of users around the world.
pilif's comment was absolutely relevant to discussion of the iPhone 5S launch, as one of the phone's primary new features has the potential to be a massive security and privacy breach given information we've recently learned regarding Apple's close relationship with the NSA.
To quote him. Please explain how he "did no such thing"
To put it another way: the problem is not the topic. It's the tactic of derailing every other topic that people want to talk about just because you think something else is too important to be ignored. That tactic, as well-intended as it might be, has a history of driving good users away from once-good fora precisely because it's so annoying to not be able to talk about anything else.
Thank you for your succinct statement, I have very little faith we will get through this any time soon given the reaction I see on HN, Reddit and other sites where the most seemingly qualified among us to do anything cannot even comprehend how pernicious this problem is.