We've all seen alien movies. The aliens are either really nice, or they go around and mess humanity up. Aliens might be both. To compare imagine humanity is an injured animal and aliens are a little kid who try's to save us. The kid doesn't know the first thing about your physiology and horribly maims you while trying to save you. As humans we have a very limited range of what we perceive as emotion, which is our emotions. If aliens come they may not even look at us as living, because we're so different from them, and so they destroy us like we were any other obstacle like a rock or something. They also might become deliriously happy at the sound of human screams because of some evolutionary advantage on their home planet and kill humans just for the pleasure of hearing that noise and think nothing of it, just like we don't think about cocaine when we inhale it. To conclude I think we seriously have to expand the way we think about aliens.
