Well, when it comes to what people say are good and bad aliens, that is not exactly a fair or accurate thing to say.
For example, I was abducted for 10 year but really abducted on a 2-3 times a month for 3 years for a specific training involving psychology, culture along other training involving technology adaptation in communication and navigation.
Its been almost 2 years since I was last abducted.
I have read into many of the abduction stories and people assume that their Aliens are bad when they are not, but because of extreme cultural differences what they might see as being good might not be the same as what someone from US or Europe might see as being good.
Trust me, I am not at all saying there is no bad Aliens but the majority of the times its just extreme cultural differences.
People don't bother to go deeper to see why they do what they do, we are used to that in most part of the Earth what they do might be seen as bad, but if you look at other parts of the world what Aliens do is actually practised in almost the same way.
Our Cultural differences are extreme, and its not even that simple, from the training I received there was a total of 4 extraterrestrial species and each one of them has an extreme cultural difference from one another.
But even within Earth, we have extreme cultural differences.
It is our Culture the reason why we are not in direct communication with them, even though our culture is progressing in a direction where we could best deal with extraterrestrial species we are still many years away from that.
We are not perfect, and we have a set of questions that we have been asked. Trust me when they say that they think we are the ones who are weird, and seeing both sides I can not understand why.
One of the biggest point is that the human species is still too unstable for being part of an interstellar community, how can we deal with extraterrestrial species when even within the human species we can't get along?