Many abductees do not remember their experience until much much later. This is what researchers describe as "lost time". i believe they are very in tune with our society as they probably created us.
Of course they would be killed if captured. Think about it as us being a herd of cattle and them being the ranchers. Do the ranchers go out into the cow field and live there with the cattle? Do they proclaim there presence on a daily basis and make sure the cattle know who they are and what they are there for? No--they simply go pluck the cattle as needed. No need to explain anything to the dumb ass cows. They serve their purpose well. Don't you think that if the cattle knew why we came for them that they would try to stop us by hurting us in some way?
You are applying the laws of nature as you understand them. Who knows what evolutionary pattern has taken effect on another planet.
The aliens don't live with us... but the ranchers certainly don't hide from the cattle. Yes the ranchers are there on a daily basis, herding the cattle into different fields for grazing, shit like that.
You think animals don't recognise death? Actually, you think we're different to animals? Animals understand far more than you give them credit for. Ask anybody that's actually worked in an abbatoir. They know alright.
I cannot follow your logic. A bunch of cows could not defeat the human race, this is why we do not need to hide. So, you're saying we could destroy these aliens?
Why then do they release people, when if all we are is cattle? Why risk letting us go so that we can remember it and tell everybody? If they created us why would they need to experiment on us? If we can destroy them why are their space crafts visible sometimes? Why are they only visible to a couple of people when there have been reports of ufo's over cities with large populations?
If Aliens have ever been involved with this planet then you're probably right they are still here. It is us, and the aliens are our ancestors.