I would have to disagree the statements about looking at human history to see how we would react to things that happen today. The mood, morals, values, ideas, customs and everything in between has changed drastically over history. The people of today would react differently to things than the people of 2000 years ago and even the people of 100 years ago. You know yourself and you know your loved ones. You have to ask yourself how you would react and how those you know well would react.
Personally I think If we discovered an alien civilization I would be shocked, excited, and anxious. The last thing on my mind would be fear or the need to conquer. I would have hope that new and exciting things were around the corner. I think I can expect similar reactions from those I know well.