The first thing you need to know before you can properly evaluate moral truth (and to some extent everything else) is that people are taught to repel truth and knowledge, because satan runs the world and teaches its standards. The rules of corruption need to be corrected. Christ focussed on this purpose relentlessly.

Mechanisms of nihilism are among the rules of corruption which the world teaches. Nihilism means closing one's mind to knowledge. It means "see no evil, speak no evil, do no evil," which is how evil is promoted. When put into a proper light, it's possible to see what's wrong with nihilism. But the world has ways of getting everything reversed by using fraudulent ways of saying things.

Consider, as one of the most important examples, the difference between negativism and positivism. People are taught, to every extent possible, to always be positive and never negative. Being positive would seem logical when looking at someone's flower garden, their hand decorated embroidery or their attempt to compete with Rembrandt. But this world is not God's garden of Eden being restored to it's original splendor, as frauds portray it. It is where sin is being overcome. While sin is being overcome, satan must be allowed to roam free, and he takes over the world and turns it into an abyss (Luke 4:6, John 12:31).

For this reason, the first task in life is not positive but negative. Overcoming sin is a negative thing, not a positive thing. It says something is wrong. That's negativism.

A good way to test moral truth is to look at examples in life. Crime is the most extreme sin, where even atheists admit it is wrong. So the "criminal justice system" teaches some lessons about morality. Is police work positive or negative? It's negative. Does it come first or last? It always comes first. Everything else is set aside until the police do what they do. This shows that the first responsibility in life is to end sin, which is a negative thing (at least in the tricky mind propaganda, where people get their heads turned upside down.)

Let's look at Christ's teaching. He said the weightier matters in life are law, justice, mercy and good faith (Mat 23:23). Law, justice and mercy are correcting wrongs, like the police do. Good faith is almost too mentally challenging to analyze, though I make the attempt elsewhere. Before the law, justice and mercy can be produced, someone has to say something is wrong, which is negativism. Most of what Christ taught was that type of negativism. Christ is the model of how people should be; satan is the model of how people should not be.

One of the key bits of information, at the foundation of morality, is the nature of sin. Worldly and corrupt persons assume sin is someone else's values. But the truth is that it all happens in their own minds. Sin puts them in conflict with the universe. As a result, they fight a war against the universe trying to turn the truth around. It's what's in the minds of the perpetrators which determine their sin, not someone else's opinion about it.