alt Hacker NewsColossus was not a panopticon, it was operating on limited intelligence and information about the world. Now, consider a hypothetical secret and clandestine science and engineering team (think: Black Mesa East) could exist completely hidden from Colossus and fabricate a workable fission bomb, then place and detonate it somewhere as a false-flag attack that Colossus would act against.
...or even just from recent middle-eastern history: an outrageous death-cult militant faction like ISIS.
Colossus didn’t have infinite intelligence, so it might be possible to hide an effort like that. Not trivial though, as it would have satellite surveillance and likely cooperation from governments who fear what it could do as a retribution. This incentive should be sufficient to make governments police violent activist groups.