A lot of movies from the 1950s and 1960s were very influenced by the Cold War and fear of atomic power -- aliens from space stood in for the evil forces of Communism and giant bugs for fear of the atom bomb. It was a very xenophobic time.
... because the outer space aliens really represented communists and they were fighting inhuman communists back in the '50's
because when the earlier films were made space travel was in its infancy,space was very much an unknown element.we fear the unknown.when ETwas made the usa had opened dialogue with the greys+had a treaty with them allowing them hassle free underground ba<x>ses+to carry on with their abductions,up to an agreed amount,in return for technology.then the usa discovered that the greys were abducting far more people than agreed,+the movies reflected the tension with big bad aliens again.The greys are the aliens responsible for most abductions,around 4-41/2 feet tall,spindly+a hive mentality.They are trying to create a human grey hybrid because their dna is collapsing.
My grandchildren were terrified of ET...had nightmares....so even though it wasn't violent it was very deeply disturbing to them. I was disappointed because i liked the movie.
Scifi movies are really metaphors of the times they were made, aliens are those that are not like 'us' so when times are good aliens tend to be good and friendly, when times are bad they tend to be evil.