Interesting idea. Impressive technology. I don't see the problem. Its not a real being, its not a ghost. Its a generated image. it has no life, no feelings, no brain etc etc. It is simply a prop, no more, no less. It is not a performer and isn't the person it represents.
When its done in film, no one takes any issue, its simply because the technology being used on stage makes it look more real, when actually, its no different.
Its like people who say that video games are far more violent now than 20 years ago. They aren't at all, intact the opposite is often the case. Its just the tech has improved to make it look more real.