I understand why people are so afraid of alien contact and being suspicious of it, but you guys are using a terrible example to theorize what would happen. You guys say it's like Columbus, I would say it's more like us now. There are tribes left on earth that we don't have contact with, we study them, and observe what they might do, but really don't interact with them. Maybe the aliens want to make contact, then it will be like the tribes we have contact with. We don't destroy them, we again study and observe them but through contact. Why would a species that has mastered space flight come to a planet and say "hey look intelligent life, lets conquer it". If we now have gotten past this point in our evolution, why haven't they? Maybe they want resources, well we can try to give them resources but we are running out for ourselves, not like we have enough to keep them alive. There are probably more planets in space with water than there are with intelligent life.