The keyword here being progress. We have been put on this earth to learn lessons and progress, we only progress through learning these lessons. The lessons to be learnt are things like Love, Kindness, Patience, Humility, Understanding, Sympathy, Empathy, Selflessness, etc. In order to learn these lessons we have to put on a physical body and come down to the "earth school".
Some learn faster than others and soon progress, those that fail to learn or simply do not wish to learn are retarded in their progress. They remain in the spirit world and like naughty boys terrorise those that do wish to learn. They 'bully' them, scare them, cause then to do harm to others. They even in some instances take over the body - the 'school uniform' and co-habitate the body with the 'lawful', original owner. In other instances they completely take over the body and do not allow the original 'owner' access at all. They have complete disregard for rules, laws or even decency. They have not yet learnt the lessons of Love, Compassion, Kindness, etc. so they are not loving, compassionate, kind, etc. In time they will soon become tired of their ways as they realise they are being left behind in progress and begin to want to learn themselves. When this happens they cease to become 'evil' and work towards and strive for self-betterment and improvement.
These souls cannot and will not remain forever evil and unchanging. No soul can remain in a state of non-progression for ever, eventually the need to improve will arise and their journey will begin. Almost on a daily basis in the spirit world you can see the 'evil' ones turning in their point of view. Yes, there are still a great many out there who need to improve, but there are far less right now than there were a great many years ago.
