Example:
Covid does not hate you, nor does it love you, it simply follows an optimisation algorithm — that of genetic evolution — for the maximum reproductive success, and does so without regard to the damage it causes your body while it consumes you for parts.
Covid is pretty stupid, it's just a virus.
And yet: I've heard the mutation rate is 3.8 × 10e−6 / nucleotide / cycle, and at about 30,000 base pairs and 10e9 to 1e11 virons in an infected person, so that's ~1e8-1e10 mutations per reproductive cycle in an infected person, and that the replication cycle duration is about 10 hours. Such mutations are both how it got to harm us in the first place, why vaccination isn't once-and-done, and this logic also applies to all the other diseases in the world (including bacterial ones, which is why people are worried about bacterial resistance).
As an existence proof, Covid shows how an agent going off and doing its own thing, if it does it well enough, doesn't even need to be smart to kill a percentage point or so of the human species *by accident*.
The hope is that AI will be smart enough that we can tell it: humans (and the things we value) are not an allowed source of parts. The danger happens well before it's that smart… and that even when it is that smart, we may well not be smart enough to describe all the things we value, accurately, and without bugs/loopholes in our descriptions.