Generally, I agree with you. And with theists, the issue isn't just "objective" morality but an "absolute" one.

However, as paradoxical as it might seem, I explore the possibility of objective moral values, on purely secular grounds, of course, and I do so by noting the overlap between scientific objectification and the aesthetic stance towards art. As Kant said, aesthetic appreciation is a form of disinterest, meaning that it involves detachment from your personal concerns to focus on the superficial minutiae of phenomena. The difference, then, is that scientists posit hidden causes whereas art appreciators might focus more on relative superficialities. Still, the question for me is whether certain values pop out of the strictly scientific picture of the objective world. I think pantheistic values might do so.