Both A and B are true, and exist side-by-side in the film.
Lowell accomplishes a good...very badly, if that makes sense. And he is not just a wanton murderer, as his expressions of guilty conscience reveal. Rather, he is a fully-dimensional character who both commits a great right and a great wrong. He is a flawed, fallible human being.
The ecosystem of the Valley Forge is -- again -- unbalanced by Lowell's choices. He then keeps programming and re-programming the surviving maintenance drones to better serve his personal needs. To serve as his doctors (for an impromptu surgery), to play games with him, to garden for him.
This is a metaphor for man's treatment of nature: it must service us and adapt to us, even as our needs change and evolve. Lowell is thus no better and no less capricious than the men down on Earth who were begging God for forgiveness one day and then nuking the last forests the next.
The forests would have died long ago without man's technology. In some senses, that's the example of harmony man should and could emulate: building and re-building eco-systems in balance. From its first evocative shot of nature in extreme-close-up harmony, Silent Running,concerns the way that man balances or unbalances his environs, whether on Earth or aboard the Valley Forge. That's the takeaway message.
The movie is basically a one-man show, with Dern interacting, sometimes wildly, with the drones and even the forest. Silent Running boasts its own sometimes-mellow, sometimes-hysterical rhythm too, a rhythm augmented by Joan Baez's musical performances of ""Rejoice in the Sun" and "Silent Running."
I can't recall many times that folk music has accompanied grand outer space vistas (outside of the ironic use of "Benson, Arizona" in Dark Star ), but the musical compositions and lyrics here strike just the right note of individual personality, sadness and wistfulness. The songs ably support the film's episodic, elegiac, and eccentric story-telling style and structure.
Given Trumball's incredible talent and experience on 2001: A Space Odyssey, it probably goes without saying that the special effects sequences in Silent Running are extraordinary. This effects work brilliantly holds up today, and the Saturn's ring sequence remains a highlight of the film. Perhaps most importantly, the exterior views of the film's central location, Valley Forge, remain totally convincing, and totally realistic. These sequences were later used -- over five years later -- in Battlestar Galactica.
In the end, Silent Running, I think, concerns man's lack of wisdom controlling the world and creatures around him. That stance applies equally to nature and technology, given the film's narrative details. And the movie even ends on a poetic apex, one not easily forgotten. Freeman Lowell -- just minutes before committing suicide -- describes a youthful experience placing a note inside a bottle and tossing it into the ocean; wondering if anyone will ever find it and read the note.
As the film makes plain, Lowell has done the same thing on Valley Forge, but on a much grander scale. He has sent a forest in a bottle of sorts, across the void of space...hoping someone will find it, and treasure it.
It's up to future man -- hopefully on a better, more balanced track -- to find that lonely, lost bottle and remember the gift he has foolishly rejected and actively sought to destroy The emotional folk songs sung by Baez speak of "sorrow running deep" at the loss of a great treasure, and the film concludes on the lonely image of a solitary drone -- with watering can -- tending to mankind's forsaken wards. It is an image that suggests environment and technology going on and on, but without man.
So Silent Running is a film about a world of "no more beauty," and "no more imagination," in which "nobody cares" about what God or Mother Nature gave us to care for. But the film leaves open the possibility of hope that it won't always be that way.
Or, as Freeman Lowell says, "Don't you think it's time that someone should have a dream again?"