Methodological Naturalism and Morality No.
Morality is not based on language use.
I can make an able judgement using my eyes, and never speak in a language.
It's a hot subject, we may not 'hold a valid position' about morality unless we first settle the debate on what it is.
I believe morality is based on judgement; as to what the optimal course of action is.
We can't make video games, without consuming resources; a moral position would be to make sure we own enough resource and keep a stable continuum. Immorally, just make games anyway, don't care about resource consumption.
My authority, and the way the universe works, is what makes it moral. Conscious beings can freely be evil in this universe, we can debate forever if there is good and evil, but when our resources run dry it's kaput.
What could possibly make you, free-to-do-evil, respect my judgement? Nothing while you've face planted into your device screen. If someone tried to take it away from you, would you complain? Come on, put on a brave face.
What I'm trying to suggest is it's a tough one to reach an agreement on but those who can agree have better odds.
Moral people; We'll always have resources lest a massive disaster.
Immoral people: We'll just keep consuming till we die.
Moral people have chosen the optimal course of action given resources, through the authoritive catalyst(s) who take those people forward.
I'm saying this action is good, this is why, blah blah, nothing else is saying keeping resources is good unless you deter pain or desire pleasure.
Is there a common moral code we can all follow? Yes, but it requires everyone is purely good willed.
Hard to find in such an abstract civilization that tempts and distracts us.
If civilization wasn't so and so evil, we'd be more moral, and naturally, these good things would happen, almost automatically.
Maybe some higher power agrees? What value is lost otherwise?
(I understand some of this is wrong but I hope you can see through to what's implied, ironically).