See, but every other time in human history that we've been scared and killed as a reaction, we still assumed superiority. We were scared because of the unknown, not because of an assumption that our new enemies (native americans, foreign immigrants, what have you) were better than us. With aliens from outer space, I think that humans would automatically assume that they were far more powerful than us, if for no other reason than that is they have been portrayed in popular cultures for centuries. And it wouldn't necessarily be an unwarranted belief. In the example, the fact that the aliens found us means that they had the technology to travel across galaxies, while we do not. That would automatically give them an advantage over us, and create the picture (true or not) that they were far more powerfully. Now, if we were the ones to travel galatically and came across aliens, that would be a different story.