I find it very revealing that so many people labeled psychotic have experiences with 'aliens'. In my opinion, after having dealt with these entities for decades, I believe they are, for the most part, malevolent. Some may seem nice and even helpful but, as the Bible says, even Satan can appear as an angel of light. My personal view is that they 'feed' off of our emotional energy; and negative emotions are usually quite strong so the fear involved with interacting with them must be quite a meal. I also think that they are the same beings described throughout history as 'trolls', 'demons' etc. Read up on the descriptions of these beings over 1000s of years and in all different cultures; there are many similarities.
I do think too that many of us are more open and prone to see these beings because we are in the process of evolving. I think as our brains/minds evolve we will have a better understanding as to what they are as well as to what their true agenda is. I believe it to be the same battle between good and evil, light and dark that we, as humans, have dealt with since our beginning.