> But if you sincerely believe it's not a game, then you're being cruel (or righteous, if you think the aliens are evil), even though it isn't real.

let me stop you right there. you're making a lot of assumptions about the shapes life can take. encountering and fighting a grey goo or tyrannid invasion wouldn't have a moral quality any more than it does when a man fights a hungry bear in the woods

it's just nature, eat or get eaten.

if we encounter space monks then we'll talk about morality