It would seem like this particular subject is easy to break down, but life has shown me that this is not the case at all. In other words, the very idea of tackling this subject, having a conversation with someone about it, can be triggering and for reasons that actually make a lot of sense.
Divine Morality
On one hand we have people who are convinced that morality is divine, given to us by our creator as a compass that points north. This particular assessment requires a lot of clearing up, at least from a logical point of view, but it's not necessarily something that anyone who practices honesty can say they know to be true or not. That, is not a controversial statement, or at least it should not be.
Where the lines get blurry, if we are to believe that morality comes from a divine source is when we try to pin point the source itself. We can say it's God, but that would mean that those who've not picked the right God, should not be moral by default, and of course that is not only incorrect, but very dishonest. Even today, we stand to find thousands of different religions in the world, with twenty or so being called the main religions or belief systems, and some of them as you might know are polytheistic which makes this conundrum of locating the source of our morality, a very difficult task.
Now I should say, just in case my position on this matter is not very clear, that I do not claim to know the answer here. This is not to say I don't hold a position, but rather that I'm very open to the possibility of being wrong, since nothing is clear as day. I can accept moral teachings being imparted to our young through belief systems, but it's precisely because of the commonalities in them, across cultures, backgrounds and Gods that I find the subject unresolved.
Secular Morality
If I stick to analyzing this subject in a completely logical manner, I do find myself finding a more cohesive dynamic at play. This is to say that its easier for me to speculate how some of our behaviors evolved and understand why today we share these common behavioral traits.
What is very difficult for those who refuse to entertain the very idea of secular morality, at least from what I've observed, is the lack of accountability. Not having an agent who is judging the actions or lack thereof makes in their eyes the very concept flawed.
If we are to talk about Secular Morality, we should try to think about social advantage and herd hierarchies too, even though these ideas seem a little blunt and lacking luster. This is to say that if we can think of reasons why being moral, acting in the benefit of the family nucleus, the tribe, the town, etc, gives an individual social advantage, leverage if you will, and a place within that social dynamic, and how this would facilitate an easier existence for this individual, we might be looking at the whole picture, although simplified of course.
The rebuttal to this analysis is very valid, and if you are thinking of it at this very moment, allow me to continue for a second. Yes, acts of immorality do give individuals advantage, things like stealing, lying, etc, can grant great advantage to a member of a social circle but we can't dismiss one very important thing here: risk. I can only equate it gambling as it seems to resemble it in more ways than one, but instead of losing money, or just money, they stand to lose rights, social value, meaning and of course a position within the social hierarchy.
Not perfect
Whether you hold a or b, both concepts are not in any way shape or form, silver bullets that have been able to slay all bad behaviors. But as incredible as it may sound, history has shown us that morality has always been evolving and moving in the right direction, regardless of the system used to justify it's logical infrastructure so to speak.
Only a few decades ago women could not vote, races where not equal, etc. So it's undeniable that even though things are not perfect, we are making progress towards a better society. Now, how we make these steps, how we continue to fine tune a social system where equal opportunity for all, where corruption is close to extinct and so on, is the very reason why ironically we fight and argue so much.