Just because you can't see the destructive nature of a technology does not mean it doesn't have one. Sometimes it's a matter of perspective and context.
When gunpowder was invented the purpose was medicinal, three centuries later we had cannons.
Many things in our world seem positive on the onset, but give it some time and start looking from different angles and you're bound to find some potentially detrimental use.
Granted some inventions like nuclear energy and nitroglycerin, both intended for constructive purposes, have a more obvious destructive potential. An example that better connects with your question is a company such as Monsanto.
Turning sand in to grass - this sounds like a great thing doesn't it?
It's for golf courses - there are amazing golf courses in dubai that required genetically modified burmuda grass in a sandy synthetic fertilized substrate. They take huge leaf blowers and cover football fields worth of sand with it, water the HELL out of it, and pretty soon, beautiful grass in the desert.
Grass in the desert is great for everyone, that wants to golf or make money off golfers.
Getting grass where it isn't sustainable is not benevolent.
Regarding the original statement I was criticizing: Of course one can construct an argument of technology itself not having an ethical bias and the notion that everything can be used as a weapon. Sure, beat someone to death with flowers, go on!
The point I'm trying to make is that I consider this tactic a distraction. Nothing more than look! a three headed monkey behind you!
Reminds me of Frank Herbert's "Dune", where the greening of the desert was viewed as ecological destruction (and more), as it destroyed the habitat of the worms.
I can't find a reference but there was a story about a drummer or bugler or something in an army, and when his side was defeated the opposing prince was about to kill him, and he said "No, I have done you no harm! I never bore weapons against you, I only played my instrument so my friends would be encouraged."
And the prince said "by aiding them you killed my men" and slew the man.
And then the prince also killed the blacksmiths, because they made swords, and the farmers because their crops had fed the army, and cobbler because they made boots that people in the army wore, and the lumberjacks because their trees were used to construct siege engine, and the cattle herders because their oxen had been used to pull the army supply wagons, and the printers because their printing presses had been used to encourage the army, and the weavers because their cloth and clothed the army, and the tailors, because they had sewed clothes for the army, and the dye makers because their dye had colored the flags and uniforms of the army, and the tanners because their leather had been used to make the saddles for the cavalry, and the merchants because their money and taxes and paid for the state to have the army.
And then the people in the next town all got together and said, "Let us all work together and see that this prince is never able to defeat our army."
Here's a thought, what if you can get the same substance to work on the sand part of concrete?? It assumes more research and work, but the argument has a kernel of truth.. I don't sure I agree with using that to not think about the ethics of what you do, but nevertheless.
You can't imagine any way terraforming sand dunes on mass scale might do damage to nearby countries? It would be akin to diverting a river upstream which was an act of war historically.
To me this argument that "anything can be used in evil ways" is a poor excuse used to distract from the issue.