I admit, I was "touched" by the heartfelt environmental message of "Silent Running" when I first saw it... about 45 years ago, when I was 12 years old. And that's about the level of education and gullibility required to appreciate this "classic" cornball flick.
Yes, the film stood out for some elaborate but ultimately bland spaceship models, some amazing droid practical effects, and for Bruce Dern's performance as the homicidal botanist, Freeman Lowell (up until that time, Dern typically played heavies in western films).
But the rest of the movie was bad. Early 1970s space opera bad; PDQ Bach musical score bad; Joan Baez wailing some ridiculous environmental lyrics bad.
Sure, Doug Trumbull was the effects supervisor on "2001: A Space Odyssey" five years earlier, but that experience in no way qualified Trumbull to direct a full movie.
That much is obvious.
Essentially, this movie asks you to forgive the lonely botanist, Freeman Lowell, for murdering three of his shipmates because the homicides were committed out of Lowell's love of Nature.
So, the primary message of "Silent Running" is that humanity is the enemy of Nature, and that humanity should be eradicated in order to save Nature, and that Freeman Lowell is a hero in spite of the fact that he murdered three men.
Which is a psychotic message, at the very least, but that's the message this film is sending.