You may have a point that is not about mass migration...
...however, what I responded to was:
"A couple posters expressed their disbelief at the possibility of moving
large numbers of people [billions of people] off Planet Earth.
Now, I would agree with the idea that "The reason" for going into
space should not be to lower the population on Earth, but instead my point was that it could be "a reason" to do so."
Now I don't really expect Geoff to have the clarity to recall what he said in his prior post, nor to figure it out when his nose is rubbed in it. But you should be able to put it together.