Many Christian apologists argue that God's statutes (laid out in the Bible, of course) are "objective morality" and thus universally true and perfect, and they argue against "subjective morality" pretty much considering it ethically abhorrent (because, according to them, it would justify people doing whatever evil they want.)
There are many things wrong with this argument, and their very definitions of these concepts. Here are the two major ones:
Firstly, they don't seem to understand what "objective" means. When they talk about "objective morality" in this context, they seem to think that "objective" is something similar to a law of physics: In other words, something that's an absolute and inherent immutable feature of our reality, and is so completely regardless of us, something that would be true even if we (or any living being whatsoever) existed at all. A bit like the law of gravitation, or the law of electric charge: These exist in this universe completely regardless of anything, and are hard immutable characteristics of it, ie. they are laws of physics.
That's not what "objective" means. If you look at any dictionary definition, in this context "objective" means "not influenced by personal feelings, interpretations, or prejudice; based on facts; unbiased."
In other words, an "objective moral" is not something that's an inherent part of the properties of this universe that exists independently for us and is always the identically the same everywhere at all times regardless of anything. It's simply a moral that's not based on feelings, emotions and biased interpretations, but instead it's arguably based on unbiased interpretation of hard facts.
The thing is: Two different incompatible sets of morals can both be "objective", and there is no contradiction in this. "Objective" does not mean "universal", in other words, inherently and by necessity exactly the same for everybody, regardless of anything. "Objective" means that it's based on unbiased interpretation of facts rather than the result of personal feelings and subjective interpretations. Different things can be factually true for different cultures, for example based on their geographical location, geographic features, the environment, the local culture, and the history of the culture. For example, it can be factually true that the place suffers from yearly floods, and this may shape the moral code of the people living there. In a completely different place it may be factually true that they suffer from regular drought, and this also shapes the moral code of the people living there, and these two moral codes may be different and in some ways even incompatible, because they apply to that particular people in that particular place. Both can be a fully objective set of morals without any subjectivity: It's just that those morals are dictated by different facts caused by the different circumstances.
"Objective morality" is not by necessity universal, the exact same everywhere regardless of anything. Different (and even incompatible) sets of morals can both be "objective" at the same time. There is no contradiction here.
Secondly, these Christian apologists always contrast the two options at their most extreme: In other words, their argument is that either there is a strict set of objective morality that's universal, strict, immutable and the same for everybody, or alternatively there's "subjective morality" which, according to them, means that anybody can do whatever they want without any limits whatsoever. That's it. Those are the two only options. There's nothing in between.
This is a false dichotomy.
Morality does not work that way. In actual reality there are degrees of objectiveness / subjectiveness when it comes to ethics and morality. It's a gradation. It's not a situation where there are only two possibilities and, particularly, those two options are the absolute extremes and nothing else.
This is the reason why, for example, most laws in most countries dictate a range of possible punishments for crimes. While "guilty" vs "not guilty" may be a true dichotomy when it comes to the legal system, the punishment if found guilty is usually a gradation, with minimum and maximum sentences. The actual sentence is chosen according to the severity of the crime. In other words, how wrong and harmful the action was. It may have been objectively wrong, but its severity may vary. There aren't only two extreme options: Either let the accused to free, or always inflict maximum punishment.
"Objective morality", as these Christians wrongly define it, would require only those two options to be viable: Either not guilty, or maximum punishment. Nothing in between.
Even in non-legal settings morality is a gradation, not just a dichotomy of two extremes. There are always degrees of how "right" or "wrong" something is. For example pushing someone may be very wrong in some circumstances, a bit reproachable but not completely despicable in others, and completely acceptable and even a good action in others (for example if it saves someone's life.) Context always matters.
And yes, there is a lot of morality that's up to subjective feelings and interpretations. It can be considered highly improper to exhibit bad manners and bad behavior in certain situations, but how "wrong" it is, that's often up to personal opinion and customs. There are genuinely things where the "wrongness" of some action is very much up to personal opinion and personal preferences, and thus being highly subjective.
With most actions, however, the degree of "objectiveness" of how "wrong" they are is much more of a gradation. The "wrongness" of some actions are more up to opinion, with other actions it's more objective, and there are enough things that humans can do to fill up the entire line from one end to the other. The line where actions become so wrong that even laws have to be passed to criminalize them is, perhaps ironically, a mix of objectivity and, to certain degree, also subjectivity, depending a bit on the local culture and customs. And that is, as mentioned before, where the severity of the punishment kicks in, with "minimum" and "maximum" sentences that can vary quite wildly.
