This is just a bunch of idle speculation. We can't speculate on the motives of aliens at all. Look at how hard it is to discern the motives of other humans, and now tell me you're going to discern the motives of something biologically completely unlike us? You can't assume they're rational motives either. Why should aliens be incapable of something like religion, egotism, mass delusion, or hedonic desires? As far as…
I think the question would be if irrationality, egoism, delusion, and hedonism allows (or prevents) a species to advanced to FTL travel.
They might also have an idea that the only life that should exist in this universe is theirs. Or they might believe that connecting with all other sentient beings is a primary goal in existence. Or they might be incredibly altruistic and want to help and benefit all others.
Though the author's other points are all valid... There is no reason to invade this planet for its resources when a few asteroids in their own solar system contains everything they need.