Like all technology, it can be used for good or evil. Same as it ever was.
Instead of going dark, you could have also said "Sounds like the killer app for circumventing national firewalls in authoritarian countries". or "Sounds like the killer app for securing confidential data from hackers". or "Sounds like the killer app for untraceably moving value between people at scale".
Instead of going dark, you could have also said "Sounds like the killer app for circumventing national firewalls in authoritarian countries". or "Sounds like the killer app for securing confidential data from hackers". or "Sounds like the killer app for untraceably moving value between people at scale".