Sounds like quite the fitting metaphor for the way humanity typically reacts to "foreigners" of any kind.
I suppose I just displayed that same level of thinking basing my whole opinion on just what I saw on the surface. But how nice to have an explanation as the one you have provided :)
My "belief" in what "they" might be like is that they would be peaceful but not stupid. To be able to travel intergalactically, would mean a fundamental understanding of the universe and the abundant energy source that would need to be tapped into. That's something we are only beginning to scrape the surface of. This same "energy" is what creates all there is and if you can really understand that on a fundamental level then you must come to the knowing that all is Creation and destruction is an unnatural force.
Sure, it's no guarantee, but some things require a bit of faith.
"We are not human beings having a spiritual experience; we are spiritual beings having a human experience"—Pierre Teilhard de Chardin