Currently, talking to a face is the ultimate guarantee that you are communicating with a human (and on a subconscious level makes you try to relate, empathise, etc.). If humanoid robot technology eventually surpasses the Uncanny Valley, discovering that I'm talking to a humanoid with an LLM and that my intuitions had been betrayed would undermine the instinctive trust I give to the other party when I see a human face. This would degrade my social interactions across the board, because I'd live in constant suspicion that the humans I was talking to weren't actually human.

It is for this reason I think it should be the law that humanoid robots must be clearly differentiated from humans. Or at least that people should have the right to opt out from encountering realistic-looking humanoids.