Obviously the people who think LLMs should be forbidden from this use-case would think it should be forbidden from put-it-in-a-doll use-case.
We routinely give our children ibuprofen or acetaminophen, this does not imply that some vicodin or oxycontin would be fine.
I think it's a reasonable assumption that a fundamental skill of being a good social creature (which we know to be absolutely critical to good human health) is to be able to distinguish between human and non-human. Or more generally conscious and non-conscious.
You are basing your opinion off of e.g. anthropomorphizing cars or dolls which 1) are obviously not human, and 2) rely on the fairly intense imagination of the anthropomorphizer to "work." Once the imagination stops, the anthropomorphization stops.
In contrast, LLMs successfully delude even intelligent adults into anthropomorphizing them. This is especially problematic for a generation of humans that grow up where most of their human-to-human communication happens intermediated by technology, i.e. LLM-originated interaction looks more human every day, but also human-originated interaction looks more LLM- (or technology-)originated every day too.
We've been living with this pathology for a while now in the form of people treating those humans on the other side of a chatbox vastly worse than they would ever treat a human face to face. Now this is chewing away at the distinction from the other end too.