The burden of proof is on you, jenny. Prove, one objective moral truth.
OK, I'll develop a "proof" for you after dinner. Note: I'm saying that objective truth is a fact of the world, so the "fact vs. value dichotomy" doesn't apply. All I'm saying is that the best moral system for humans to live under is something that we should all be able to agree on by referring to objective facts of history, etc.
Postmodernists & creationists say that morality is just a social construction (accepted tradition of a particular group, subjective whim, etc.) that's not tied to anything inherently valuable about being a human being. Therefore the world could never converge on a common set of moral codes. It'll always be Hobbes' war of all against all. (The only way the world could converge on one set of accepted truths is by the sheer force & ruthlessness of the victorious interest group.)
Each one of us has a rational mind. We decide how to act based on what we understand about our world, and what we predict what will be the result (both immediate & long-term) of our actions. We judge these results in terms of how well they maximize that which we value.
None of us is able to directly inject our thoughts into another's brain (as in mental telepathy). We can only indirectly influence other people's thoughts by talking to them, by letting our behavior set an example, by physical force, etc. To the other person, our attempt to modify their behavior is just another fact of the outside world, competing with all the other things they know or theorize about how the world works. They form their own judgements about what we're trying to get them to do. They judge our reputation for honesty & wisdom; they judge possible reasons for why we would lie to or manipulate them, and they judge what might be the outcome if they follow our suggestion.
In short: People have free will. Therefore each one of us is a moral actor.
In order for a collective to be a moral actor, the individuals who make up the collective would have to lose their moral responsibilities. But since moral responsibility comes from having free will, which comes from having rational minds with the capability of making judgements, this means they'd have to give up their ability to think rationally.
But history shows that this is impossible for most people to accomplish. Some people willingly join cults where they suppress their instict for judgement because of their devotion to the cult leader. Cults almost always remove themselves from society in order to limit what the followers know about the outside world. Many cults are organized around tightly-knit communal housing arrangements, where there are built-in psychological pressures for conformity.
The vast majority of people rebel at the notion of giving up their free will. This is why cult leaders must go to great lengths to build & sustain an environment where their followers will continue to follow the leader's will against their better judgement.
Slavery has always needed a system of dehumanizing the slaves in order to survive. Thus it was illegal to teach a slave to read & write. And even after the importation of slaves was made illegal - so that eventually most slaves had been born into slavery and had no direct knowledge of any other way to live - the slave system was still sustained by the constant use of force.
Thirdly there are the collective systems of the 20th Century. Communism, fascism, & Naziism were collectivist ideologies that believed that groups, not individuals are the true moral actors. (Respectively, the economic class, the nation, & the biological race.) They all failed rather spectacularly. They all were forced to spend constant effort on sustaining varying degrees of physical terror and isolation (where propaganda took the place of real knowledge) to keep their people from rebelling. The one system that lasted for decades - Communism - was left in the dust economically by the system that's based on moral individualism - capitalism.