Alright. Let's follow through.
What is your epistemology of morality?
I will mainly focus on my view of morality and why I think that it offers a better explanation than objective morality. Regardless of whether you support one view or the other, I think we can both agree that moral conflicts between humans exist, like "is it morally wrong to murder?" some think it is, while other don't, for whatever reason.
First I would like to point out what I believe to be some of the biggest issues with objective morality, both when it comes to a God, but also when no God is involved, which I think a subjective morality solves.
We know that people all around the world holds a lot of different religious views with different ideas of what a God is. Yet it is not uncommon for them to claim that their God is the author of objective morality. Now let's assume we have two different religions with different rules, both of which advocate that people should live in accordance with their Gods rules, because these are what is objectively correct.
The problem occurs since both religions claim a different God to be the author of objective morality, which means that both of them can't be correct. In fact, if one religion is true could mean that the people of the other religion would be kill for breaking certain rules set by this God. Yet both of these religions claim that a God best explain objective morality, but this is only true from their perspective, with the assumption that they chose the correct God. But none of them is capable of proving their God to be more correct than the other, which means that they can't demonstrate that the objective morality that they claim is from God, is in fact from their particular God and therefore also incapable of demonstrating that the objective morals are even true to begin with, there is no valid foundation for making such claim. Which to me means that they end up in much the same problem as atheists does, when they claim that objective morality exists, because they as well can't point or demonstrate who this author should be. The difference between atheists and believers in this case, is that the believers at least vaguely can point to a God, despite it not really offering a valid solution.
As I established above and that we hopefully agree upon, is that people have different opinions on what is considered morally right and wrong. So we could ask our self the following question, "What would we expect to see, if we have a lot of different people with different ideas of what is right and wrong?", a reasonable explanation is that we would see people group together with other people, which best match their own views on what is right and wrong. For example, it would be unlikely that a person holding the belief that "Killing animals is wrong" would prefer to go the group that hold the view that "Killing animals is fine".
Which means that if morality is subjective, it is perfectly explainable why you would have different religious groups with different ideas of what a God is and what rules such God have made. When such group is convinced about the validity of their God, it's not really a huge leap to then also claim that this God is the author of the morality held by this group as being objectively true, after all their God is true and the creator of everything.
So if there is no objective morality, why don't we just run around and kill and rape each other like crazy?
To me this is best explained through instincts and human being social animals, I don't think anyone would deny this, given that we live together packed in "boxes" stacked on top of each other in huge cities, which I don't think we would see, if we didn't like to socialize with each other.
In regards to instincts, we as other lifeforms seem to share a instinctively behaviour of trying to survive, I don't think anyone would expect to see an antelope freely walking into a herd of lions, we might see certain animals such as elephants given their size chase them away etc. So it obviously depend on the type of animal.
Humans have not always been on the top of the food chain, in fact we as a lot of other animals have suffered under the same conditions as them of being killed by these predators. Humans are extremely vulnerable, we are not fast and our natural defence (lack of claws, strength, deadly teeth, poison etc.) is arguable amongst the worse in the animal kingdom for an animal of our size, meaning that if we went head to head with a lion, we would probably lose close to a 100% of the time.
The development of the brain is what give humans an edge, but the brain is extremely slow when it comes to developing, as it takes a long time. But not only that, human pregnancy takes a long time and doesn't exactly improve a female chance of surviving, if she couldn't rely on a group to help her. Even when our children are born, it take years before they are capable of taking care of themselves. So for us to survive we need other humans, the larger the group, the stronger it is, as you have more people to rely on. But living in groups creates conflicts as we don't agree on everything, exactly as we see it in other animals, they fight and kill each other as well. But given the brain of humans we have the ability of complex language which allow us to communicate more effectively, and have evolved over time. So a lot of issues can be solved without fighting.
Also given how vulnerable we are, having trust in each other appears to me to be natural, which obviously lead to what we call morality and ethics. If we couldn't trust each other, no parent would drop off their child to a daycare center, without constantly worrying about whether their child had been killed or hurt, while they were away. But trust is not simply something you decide to go with, it falls on some basic ideas, such as lying is bad, if you tell me that you will take care of my child and then you kill it while im gone, surely there can't be any trust between us and other people knowing that you did it, will probably not trust you as well, since you already demonstrated that you can't be trusted. Which most likely also mean that people are less likely to help you. And since I already pointed out that humans need others to survive, it is in your best interest that others want to help you. And therefore lying to others is not beneficial for you in the long run, and especially not if you are caught doing it.
So whether you chose to lie anyway, is a judgement call you make, because we know people lie, but you might value what the lie brings you more than what potentially getting caught lying might have of consequences.
Therefore a subjective morality having developed over time through natural explanation, seem to account for why we see the differences in moral standards, both in societies, but also between individuals and sub groups within them. And that these are nothing more than agreed upon systems to maximize our chance of survival. Obviously over time as humans have evolved and developed our knowledge of the world in which we live and moved from the middle of the food chain to the top, these moral values and ideas have changed as well. But fundamentally, we are doing the same things as we did back then, rather than the hunter giving his child to his spouse, family or the those staying at the village/cave, we throw them in a daycare center or hand them off to the grandparents, while we go hunt for food at the office desk.
But looking at this process, there is nothing objective about whether you should kill or not kill, if the group you belong to see it as a benefit to steal someone else's ressources to increase your own chance of surviving, while at the same time get rid of some competition, it might be considered the right choice for that group, and they might very well think that they are in their good right to do so. Obviously over time, this have developed as well, as we might prefer to trade with each other instead, to not risk getting killed in a battle ourselves or lose it.
So at least in my opinion, simply looking at human history and how we have done things in the past, where we came from and how we manage to survive, gives a pretty good explanation of how and why morality evolved, and why we disagree with each other. Because there is no objective moral truth, but there is an instinctively idea it seems shared between all lifeforms to want to survive, and we do this is different ways, humans simply have a much more "complicated" way due to our brains than other animals have. If we didn't have the brain capacity we have, we would most likely have gone extinct or at least not have been more expanded on Earth as the other great apes are.