In the case of the napalm Grandma it seems odd to me that you're suggesting the LLM is stupid because it's answering in a way that makes sense given its prompt. The issue doesn't necessarily suggest a lack of reasoning, but that the LLM is trusting the human.
For the record, I agree with you – I would have thought that an AI that can reason well would probably know when not to trust humans, but I suppose that assumes it values preventing humans creating napalm over being correct and helpful.
Maybe it just doesn't share our values and prioritises being honest and helpful. From this perspective the issue then wouldn't be that LLM is stupid, but that they are too trusting and too honest, and that we must find a way to build an LLM that is more distrusting and deceptive if we wish to align it with our values and our nature.