The existence of an objective moral standard finds its source in God, specifically the God of the Judeo-Christian worldview.
How do you determine that the God of the Judeo-Christian worldview is the source of morality? Where is your evidence to show that? So far, this is merely an assertion until you can validate it.
This is the evidence:
1. God created man and woman in His image and in His likeness. Part of the "image bearing" quality that is unique to humans is the fact that we have an intellect (mind), emotion (feeling), will (choice), and a conscience (moral capacity).
This is also an assertion. First you must prove that God Exists, then you must prove that God actually created man in his own image and likeness.
There is no dispute we have intellect, emotion, will and a conscience... however those to not depend on a God to exist. You must prove those things come from a God, or your argument is not positive evidence, or even evidence for anything.
2. This last is what makes us particularly unique because it is reflective of His very nature.
Again, until you validate point #1, this point is similarly invalid.
3. An aspect related to this moral capacity is the ability to recognize the existence of objective moral standards which are prescriptive, perfect, objective, and universal and are evidenced by the following:
I don't recognise the existence of objective moral standards, along will millions of other people. That's why I'm asking for your evidence on the topic, so if I see the evidence, I will recognise they actually do exist.
In fact, there's no reason to assume such a standard exists at all.
A. the universality of basic moral beliefs
Basic moral beliefs are not universal. Some are more commonly held than others though.
B. the unavoidability of making moral judgments
Not all judgements are moral, or morally based.
C. the inescapability of there being a perfect standard by which we measure the imperfections in the world (we can't know injustice unless we know what is just).
There's no reason there is one universal moral standard. Many moral people still have differences of opinion on moral issues. They both recognise what is just, but what they define as just may be different.
D. the impossibility of making judgments about the progress (or regress) of the human race unless there is an external objective moral standard by which we measure the human race.
You don't base your judgements on an external source, you base them on your own opinions.
E. the fact that we make excuses for ourselves when we break the moral law.
Not always... most times when I make a mistake, I apologize for making a mistake. That also doesn't demonstrate that moral law is universal, you'd still make the same excuse if you violated your own moral code.
F. the moral guilt we suffer from breaking the moral law.
You'd feel an equal, if not greater guilt for breaking your own personal moral standard. This point also proves nothing.
G. the fact that the moral law, like the laws of mathematics, is discovered and not invented.
That's not a fact, that's an assertion. Show your evidence.
Furthermore, if your universal moral law was self-evident as you claimed, then we would be in a position to recognize it, and not discover it. That's what self-evident means.
Likewise, if we can't judge what is just without understanding this moral code... then we have never been in a position to fully, accurately judge what is just and what isn't, as you are asserting we still don't understand the moral code in full.
This point contradicts everything you have said so far.
H. the reality that we sometimes act from a sense of duty (e.g. to save a life), even when our strongest instinct to survive tells us not to risk our lives or safety to do so.
That's also no evidence for an outside source, that's evidence for how someone behaves when their instincts come into conflict. Some will choose to save the persons life, some will choose to ensure their own safety first. That's evidence of subjectivity.
I. the truth that we find some things in all cultures (like genocide or rape) that we perceive are wrong and evil.
Those aren't considered wrong and evil in all cultures. For example, the Bible, a supposedly divinely inspired work has God himself (supposedly the author of your universal morality) ordering multiple genocides, and condoning the rape of the conquered women.
Are you saying the perfect author of perfect morality would willfully violate, and order others to violate his own moral code? That proves that your God is not moral, or infallible.
J. the fact that some things we do (such as kill, lie, steal, cheat, or be disloyal), we do not want others to do to us.
That also has nothing to do with objectivity. In a Subjective system, one would obviously assume people would not want those things done to them either.
Therefore as humans, we are capable of thinking, feeling, and choosing, and also have the moral capacity to know right from wrong. As such, humans are morally responsible to the Moral Lawgiver - God, the creator.
Seeing as not one of your arguments has backing, or validity... I must write off your conclusion.
You have no demonstrated that an objective moral law exists. You have only stated that many humans share many values, then attributed those to some mystical universal law.
Still, I am open to hearing the evidence for your assertions if you possess any. But, until you can back them, they are still merely assertions and NOT evidence.