Are you not employing circular reasoning here ? Sure, shooting computer-controller opponents is ok because they don't experience any suffering from being hit by a bullet; but that only holds true if we assume they are not conscious in the first place.

Yeah. How is that circular reasoning? Seems straightforward to me: "computer-controlled opponents don't suffer from being shot -> shooting them is okay".

If they are conscious to some extent -- let's say, their Consciousness Index is 0.001, on the scale from 0 == "rock" and 1 == "human" -- then we could reasonably say that they do experience suffering to some extent.

If they are conscious to some extent, then we could reasonably say that they do experience something. Whether that something is suffering is another question. Given that "suffering" seems to be reasonably complex process that can be disabled by the right brain injury or drug, and computer NPCs aren't anywhere near the level of possessing similar cognitive functionality, I would say that shooting them still doesn't cause suffering even if they were conscious.