Can somebody give me a good argument in favor of objective morality?

[Angrboda]

I read something that says a majority (56%) of philosophers identify as moral realists.

From my perspective, morality is almost obviously subjective. Humans decide what is right and what is wrong within their own community. I can't think of a single thing that is moral or immoral today that wasn't the opposite in another time or in another culture across human history. Murder, rape, treatment of women, torture, the list goes on...all were acceptable in certain contexts at some point (and we still didagree today on the morality of a few of these things). Because the society deemed it so.

You are confusing an ontological question with an epistemological one. The one asks what is there, and the latter is the question of how we know things. One can assert the existence of objective morals without needing to assert that we thereby have complete knowledge of what those objective moral truths are. As a consequence, it's possible that the changes in our understanding of morals reflects changes in the knowledge we have of those objective moral truths, and doesn't imply the non-existence of those moral truths. So for example, it may have been thought that slavery was morally acceptable because we had a flawed understanding of the moral truths that apply to slavery. When our knowledge of the morals of slavery improved, we came to realize that it was immoral. The objective moral truths did not actually change, only our understanding of them.

And if we were not here to dictate moral rules , then there would be none at all. No animals are abiding by them,  that's for sure.

Is the ratio of the circumference of a circle to its radius not equal to Pi if there is nobody around to think of the concept? The existence of true propositions isn't necessarily dependent upon there being knowing subjects to perceive the truth of those propositions. Moral realism is the claim that there are moral propositions which are either true or false. The moral propositions would still exist, even if there is nobody to comprehend them, and by equal measure, if those moral propositions have truth content (are true or false), then moral realism would still be true. For example, if it were shown that torturing a cat is objectively immoral, it would remain so even in the absence of any cat torturers around to do the deed.

And obviously no religious text can be called objective moral law, because then we can have all sorts of fun pointing out what people in biblical times thought was perfectly fine that is appaling to us today.

You seem to be assuming the necessary truth of progress, that our current understanding is better than the understanding we had in the past. This isn't necessarily a truism. Just as it's possible to gain knowledge, it's possible to lose it. There is nothing about moral realism which entails that we necessarily have better morals today than they did in the past. Perhaps they had everything just right, and over time we have fallen into error. This is another argument similar to your first one in that the relativity of morals across time and between various cultures does not itself justify the conclusion that there are no moral truths.

A universe that was not created for us, that existed for so long before us, could possibly have within it an objective morality waiting for an advanced species to discover and implement? Seems very wrong. Am.i thinking about it in the wrong way? I'm sure there are arguments in favor that I haven't considered.

Mmmm. I think this returns us to my second objection. It also raises the very real question of what we would mean if we were to say that animals, such as chimpanzees, have morals (as evidenced by their behavior). Is our definition of what a moral truth is too "human-centric?" What ultimately does it mean when we say that we are moral beings if animals also are moral beings? What exactly is the "stuff" that makes a given proposition moral (e.g. "Killing is wrong.") and another proposition not a moral one (e.g. "Stephen Hawking was smart.")?