What logical fallacies are employed in this statement, "Good and evil must be defined by an immutable moral authority that transcends man, otherwise they are merely individual, or group preference."

What logical fallacies, if any, are employed in this statement, "Moral good and evil must be defined by an immutable moral authority that transcends man, otherwise they are merely individual, or group human preferences." I'd prefer you don't rob me, but I have no absolute moral authority to say that it is evil for you to do so.

"Moral good and evil must be defined by an immutable moral authority that transcends man, otherwise they are merely individual, or group human preferences."

It certainly is a fallacious claim because it presumes there is an

immutable moral authority that transcends man

when no evidence of such an authority exists. So, this is a religious opinion, and a very thin one at that. Basically, it is an unsupportable argument from belief, but not a logical fallacy in itself. As it is, this person assumes what has yet to be proven, but s/he would need to expand upon the claim
with a conclusion to qualify it as a classic fallacy. In other words, we'd need to see the full syllogism as he or she proposes it.

At least that's my sense of it.

The writer expresses one opinion, but there is evidence for other foundations for moral beliefs.

DeWaal argues that morality is biological. He is very persuasive (I've heard him speak). Link: www.emory.edu/EMORY_REPOR. . .

Others hold that morality is founded in group membership. I don't see why that is automatically wrong.

None of that means that morality can be rejected. The idea that morals must either be totally absolute or totally relative is a false dilemma, which is a classic fallacy.

No Logical fallacy is present; this is merely an opinion.

This is one of those claims where you'd be perfectly correct to
ask the claimant to prove it, or logically take the claim to the next step:

G-d being immutable and transcendent is the source of all morality!
Non-sequitur

Why? For one, what does immutability and transcendency have to do with morality? It's a false premise.
G-d could be immutable, transcendent and immoral, or God could be moral, but neither immutable or transcendent.

If we use the Bible as a credible source to describe God's actions he appears NOT to be altogether transcendent or immutable. In fact, He sure seems to change his mind a lot and acts quite immorally and interactive with his own creation: Cursing Adam and Eve, genocide, impregnating virgins, sending plagues, cursing all humanity for eternity, sending his own Son into the world to be mercilessly slaughtered.

If you ask me this seems to make the case against the claim more than it supports it. The burden of proof is on the claimant to explain how God is what he is claiming Him to be, and there no way to get there beyond an opinion.

God could be moral, but neither immutable nor transcendent. But how do we know this is true when all the so-called evidence leads to the contrary?

Human based morality is merely individual or group preference! Okay, but how does this make them less moral?
They're still moral even if it is a matter of individual or group preference. Or is he claiming that this makes them immoral?

Or, is he proposing,

Humans must believe in G-d to be moral, or
Human preferences whether individual or group based are immoral

Well, aren't all religions individual and group based? Are they immoral if they
don't believe in the trinity, or believe in an unconventional Godhead?

Who is the arbiter here, and which G-d are they referring to?

See, it still doesn't work.

Human-based morality is either individual or group preference.
G-d is immutable, transcendent, and the source of all morality
Therefore, individual or group preferences are immoral?

Nah, doesn't work either.

Yeah, I think you can confidently send this fellow back to do his homework. He's got a lotta 'splaining to do', Lucy.

Wow! Once again all answers are correct. The operative and undefined postulate containing, "must be defined by an immutable moral authority" is what renders the statement a non-sequitur. So it is not illogical as it doesn't have a logical structure. It is a speech act.

If the argument has the structure of a disjunctive syllogism like the following:

1. Ether moral good and evil must be defined by an immutable moral authority that transcends man, or they are merely individual, or group human preferences.
2. They are not merely individual or group human preferences.
3. Therefore, good and evil must be defined by an immutable moral authority that transcends man.

it would only commit the fallacy of false dilemma (of course, you have to show that there are more available options), or you can go and try to prove that both disjunctions are false.