Let me re-state and examine the various arguments you all have given.
- "The community creates moral truths."
I attribute this argument to Michael and Vera Mont.
It was not explicitly stated that the community creates moral truths, but that's the implication. If the community merely creates moral falsehoods, false beliefs of good/bad, what should/shouldn't exist and be done, there is no logical reason to act on them, and they are not actually good/bad. For them to actually create morality, they must actually create moral truths, or discover them.
I would like you to expand on how communities create moral truths. You're giving me an extrinsic moral truth: "morality is what the community decides is moral". Perhaps that is also the axiom. But why is this a correct axiom, or a correct implication? If everyone decided the opposite, would they still be correct? why should the community get what they label good, and not get what they label bad? If the neighboring village decided the opposite, would it then be both good and bad for X to happen/exist? Or only while in X village? I agree that communities create their own cultural opinions of good/bad - but why should anyone believe they're anything more than incorrect beliefs?
I label this argument "X being stated to be a moral truth, seeming arbitrarily, without justification".
Unless there is more reasoning I have not found, I do not see why these supposed truths are any more truthful than the moral claim that only toothpicks and paperclips should exist.
- "Certain things are bad, even though it is true that nothing is bad."
I attribute this argument to Isaac.
If there are no moral truths, every moral claim is false. If any moral claims were ever true, it would have to be the case that there do exist moral truths, because such claims would themselves be moral truths.
In such a world, calling anything "bad" does mean what it otherwise would. To say something is "bad", when bad does not exist, means very little. Perhaps it means you incorrectly believe the thing should not be done - but that would mean you do not believe there are no moral truths, because you'd believe yourself to be wrong if you did. It cannot be the case that nothing is bad but also that some things should not be done. That would mean that nothing is bad, but also that some things are bad. This breaks the laws of logic, specifically the law of noncontradiction, x =/= not-x. Nothing can correctly be called bad if the concept "bad" does not actually exist, for the same reason nothing can correctly be said to be "from the fictional universe of Star Trek". Sure, you can THINK things are from that universe - but you'd be wrong.
- "X is moral because it is my intention to cause or not cause X"
I attribute this argument to Benj69.
Does mere intention make it so something should, or shouldn't, be done? Does it make it a fact that nobody - or just you - should or should not do those things? If it is true that there are no moral truths, it must also be true that moral-based intentions cannot be true claims, merely incorrect claims about morality. If moral truths cannot exist, intentions are illogical and there is no logical reason to act on them. Also, me having the intention to torture as many people as possible would make me torturing people moral, and if I were to consciously decide not to torture it would be immoral.
- "The experience of suffering is inherently a logical reason not to continue it."
I attribute this argument to Benj69.
This is another "X being stated to be a moral truth, seeming arbitrarily, without justification". This is hedonism. I explain my reasons against it in the OP and in "The community creates moral truths". The experience of pain might seem like it has inherent bad in it, that it makes it worse for you to exist as you and therefore makes it worse for you to exist at all, but that is merely an illusion created by evolution.
- "Trial and error proves the merits and demerits of any moral principle."
I attribute this argument to NOS4A2.
Nothing can have moral merits or demerits if moral truths do not exist. You are acting as if moral truths exist, else nothing could truthfully be a merit or demerit to any given moral system or claim or principle. Moral systems, or claims, must either be self-justifying or be justified by exterior moral systems/claims. It is impossible to justify a moral system or claim using the merit/demerit system without explicit exterior (or interior, if it's a truth that does not require the merit system) moral truths. Otherwise, how would you know what constitutes a merit or demerit? Arbitrarily? By instinct?
- "That which promotes survival is that which is factually good."
I attribute this to Nils Loc.
This is another "X being stated to be a moral truth, seeming arbitrarily, without justification". There is no truthful reason why life should continue to exist, why it should not be wiped out today.
- "Morality is not about what is the case, but how we want things to be."
I attribute this to Banno.
If nothing is truthfully good or bad, there is no logical reason to want anything, therefore there is no logical reason to act on anything you want. There is no logical reason to make the world more like how you irrationally want it to be, the things you want are therefore not actually good. If you believe there are no moral truths, you must also believe there is no valid reason to want anything.