I don't really believe that there are any sort of objective moral truths. I think we can probably make normative right/wrong statements, but that's about as far as you can go.
what are the real concerns with the notion of morality being relative? you say it was morally right to kill that guy to steal his wallet? cool. the law is not relative, however, so you're still going to prison. but have fun feeling innocent. it doesn't matter, in practical terms.
So a specific example of something so simple as lying ...
Nazis are always good material for ethical dilemmas. Let's say you are living in Amsterdam in 1943. Being morally upright, you have taken in a family of Jews and hid them in your attic.
One day, there's a knock at the door. Major Hochstetter of the Gestapo is there and asks, "Are there any Jews in this house?"
Do you lie to him? Why or why not? Do you think about your own skin? Do you think about what you know will happen to the family? Do you simply not wish to lie and so tell him the truth?
You would lie.
In real life, human beings in that situation would develop a emotional and/or empathetic locality and commit to the people you are keeping safe
If you wouldn't lie and you rationalize it with some philosophical paradigm or logic.... I'm pretty sure that only a human being who's condition is affected by his/her autism would be able to to that... and even then you'd have to have some pretty high functioning autism to make a cold calculated decision