It’s certainly possible to hold values about equality and respect while also excepting a realist account of the universe. For example, using science, we can compare both similarities and differences between entities to understand which of their interests might need to be respected. In the case of a rock which has no nervous system or brain, there isn’t much evidence that it has an interest in not being kicked around, but there’s lots of evidence that a fellow human being has this interest.
It’s possible that some kind of anti-realism is true, and that everything is in our minds. It’s perhaps impossible to prove it either way. For the anti-realist view, though, they have a lot of explaining to do, e.g. why objects seems to carry on when they are not being observed, following laws of physics and such. It needs some kind of additional story, whereas the realist view that things happen independently of observers is more straight forward.
Bringing this back around to the Divine Visitor, I can see where the theory is coming from. The player observes the world only when the game is running, so when the game ends, perhaps the world no longer exists because the player is no longer observing it. It’s a classic anti-realist perspective, perhaps even solipsist, if the Divine Visitor’s mind is the only place where the Panzer Dragoon world exists. As far as it being consistent with the rest of the game, there’s a lot more explaining to do there. For a start, what would be the point of it all (freeing the world from the Towers) if that world stops existing straight afterward?