Why do flat-earthers claim the 1967 photo of Earth from space was made with CGI, even though CGI didn't exist back then?

I have never heard that. If they say the ’67 photo was CGI they used the expression to mean “faked” or “fruadulent”.

Flat earthers have used software such as photoshop to analyze that and other images.

The image was doctored. A photograph of a moon like object said to be earth was stripped into the photograph of a supposed moon scape. The square cut lines and tape marks were seen giving away the photographic fraud.

Why cant I feel anything in my sleep? I cannot even feel myself moving, breathing, and swallowing saliva! I cannot even hear anything, not even my alarm! Some people that I've been with says that I'm moving a lot in my sleep, how can I stop it?

The biggest NASA fraud giveaway is the size of earth from the moon. In the errant cosmology of heliocentricism and of the globe, the earth would be seen as extremely large on the moon. However, it is seen to be about the size of the moon, as it is seen on earth. The fraudsters are telling us that they are deceiving us. They are laying it out for the world to see. Many people still do not see the lunar landing absurdity.

In the above photo, by manipulating it in photoshop, the background in (b) can seen to show signs of having been stripped together. The actor dressed as a spaceman is photographed separately from the American flag taken together with the moon which is meant to be a small version of earth as taken from the moon.