Perhaps an analogy could clarify? Although it isn't a perfect one, I'll try to use the points of contrast to explain why it can be considered dangerous.
If a young child is really aggressive and hitting people, it's worrying even though it may not actually hurt anyone. Because the child is going to grow up, and it needs to eliminate that behavior before it's old enough to do damage by its aggression. (don't take this as a comprehensive description, just a tiny slice of cause-effect)
But the problem with AI is that we don't have continuity between today's AI and future AI. We can see that aggressive speech is easy to create by accident - Bing's Sydney output text that threatened peoples' lives. We may not be worried about aggressive speech from LLMs because it can't do damage, but similar behavior could be really dangerous from an AI which has the ability to form a model of the world based on the text it generates (in other words, it treats its output as thoughts).
But even if we remove that behavior from LLMs today, that doesn't mean aggressive behavior won't be learned by future AI, because it may be easy for aggressive behavior to emerge and we don't know how to prevent it from emerging. With a small child, we can theoretically prevent aggressive behavior from emerging in that child's adulthood with sufficient training in childhood.
It's not the same for AI - we don't know how to prevent aggression or other unaligned behavior from emerging in more advanced AI. Most counter arguments seem to come down to hoping that aggression won't emerge, or won't emerge easily. To me, that's just wishful thinking. It might be true, but it's a bit like playing Russian roulette with an unknown number of bullets in an unknown number of chambers.