@niplav I think the belief stems from how humans seem to function. People can learn to be better people (or worse people for that matter).
If humans are corrigible, then surely other intelligences could be too.
That said, are humans actually corrigible?
It's hard to prove that either way because we don't know what the terminal human values are, or even if humanity has shared terminal values, and irrational behavior sends constant mixed signals.