Ok, fair enough.

So, what you're really saying is that the aliens lack some indefinable trait that the humans consider "moral", and the humans lack a definable trait that the aliens consider moral.

This is a common scifi scenario, explored elsewhere on the site. See EG three worlds colide.

Your specific scenario seems to me to involve a highly improbable scenario where humans are considered immoral, but somehow miraculously they created something that is considered moral, and the response is to hide from the inferior immoral civilization.