How can you justify universal morality unless you can also justify that your own personal opinions are the standards of the universe?
Using reason.
There isn't an universal morality. At least those groups that make a God claim say their ethics are derived from an unchangable, eternal authority. Now, it might all be made up, the existence of ethics does not prove the existence of all these different gods, but at least ethics is something that can be internally consistent in such a system. A materialist worldview cannot allow for such internal consistency.
An non-theist morality has an easier time of being consistent than a religious one, since such a morality is more likely to be based on reason, rather than trying to rationalize what an old book says.
My understanding of morality is much clearer and makes more sense now as an atheist than as a Christian.
So, what are your universal ethics?
Well that's quite a big question which one could probably write a book on if one had time to research and write.
I'll try to explain the basis of my understanding of morality in a very simple way. If you want to know more, then ask.
1) Morality is partly a way of acting.
2) Morality is a universal good or bad, that applies to all people.
3) A universal good or bad, that applies to all people, would be considering the subjective good or bad or all individuals equally.
(eg: My wish not to die is equal to your wish not to die).
5) One of the most important parts of this morality would be respecting peoples choices over their sphere of sovereignty (eg: It is their choice what they do with their body and mind... this would disallow things like murder, rape, and assault).
If I had to give a basic principle, it would be 'Respect the will of others as equal to your own'. That is still very vague on it's own though.
I hope that makes sense as a very basic explanation.
Is abortion right or wrong?
It's acceptable because fetus' don't have a self-conscious wish to live. That's the same reason it's okay to kill most animals.
I have a longer explanation... again this is just the basic so I don't have to write too much, unless you want me to.
Are children supposed to honor their parents?
Well this isn't an issues I've thought alot about. I suppose it makes sense for children to respect their parents wishes most of the time, but there will be exceptions.
I'm not claiming to have a fully completely philosophically rigorous understanding on all moral issues. Such an understanding would take time and research, and I'm just 23.
Are people to tell the truth at all times?
Not all the time. An obvious exception would be lying to save a life.
You really think that you can answer these questions definitively so we can all be convinced that your answer is best?
I think I have a basic moral theory which has the potential to answer everything... but I haven't got through every issues, or most issues yet.