This is a false dichotomy that ignores many other options than "giving itself its instructions or taking instructions from a person".

Examples include "instructions unclear, turned the continent to gray goo to accomplish the goal" ; "lost track mid-completion, spun out of control" ; "generated random output with catastrophic results" ; "operator fell asleep on keyboard, accidently hit wrong key/combination" ; etc.

If a system with write permissions is powerful enough, things can go wrong in many other ways than "evil person used it for evil" or "system became self-aware".