I’m not surprised these parents took their children to this movie. When this came out I was 10 years old and a huge science-fiction fan. I hated horror and was deeply affected by anything scary, but the advertising for this movie was so convincing that it was a “real science fiction story,” that I convinced my father to take me to see it. I remember really pleading with him to go (the only other movie I ever saw with my dad was the Muppet Movie).
I was terrified from the moment it started. We also did not walk out - not sure why. It was a somewhat traumatizing event for me (but not as bad as when I went to see the Elephant Man).