Humans decide on what's moral within their own limited societies. A group can change its opinion at any time. Pick any behavior and I can give you an example.

Uberdem: "the larger majority of our collective society decide tomorrow that rape is morally acceptable "

1, Do you think that society is something that evolves separately from the people who comprise it? We shape society, and society shapes us. It's circular. If enough people highlight an evil, other people start to think about it, and eventually society turns against that evil. Did you not notice that modern Western societies universally condemn and outlaw hideous religious practices like genital mutilation? The society I live in is also very upset about sexual abuse of children by clergy in just about every Christian denomination. People are increasingly turning away from religion as a result. That's how society works.

What sad people you Christians must be to look inside yourselves and see slavering feral homicidal rapists restrained only by fear of your sky fairy. Truly you are made in the image of your imaginary friend. I pity you, but I don't want you anywhere near my family.

2. Hitler perverted the ideas of Darwin, and in any case his master race theory ended in total failure. Your understanding of evolution is shallow. Ever heard of symbiosis? Human evolution is especially complex. A tribe that killed all its weak members wouldn't necessarily prosper in the long-term. Weak or strong, people play all kinds of subtle roles in communities. People have known that for a long time. Societies that deliberately weeded out and destroyed the weak were rare enough to be noteworthy in history. The Spartans are one example.

What objective moral values does your cult offer? Who best represents those values? Is it the money-grubbing televangelist extracting money from the weak-minded to pay for executive jets and prostitutes? Or perhaps it's the Westboro Baptist Church with its vicious "god hates fags" message. Surely the Christian Crusaders of the middle ages were paragons of Christian virtue. But wait. The Pope told them that god would forgive any sin, however horrible, that was committed on a crusade. Their sins included rape, mass-murder and cannibalism.

Morality is a mixture of our innate instincts as primates, and our experiences in our families and society. Every individual helps to shape those morals, and every individual is shaped by them. Religion is redundant. Look at the history of societies controled by religions and tell me which one had acceptable morality?

All religious arguments for morality are human arguments. They are simply embellished with false authorship. The Ten Commandments, the Parables, the Sermon on the Mount are all human creations. They do not become "objective" by claiming they are written by god.
The fact that theists must make an argument for the "objectivity" of their moral basis proves that all moral principles must be argued for if we are to accept them as part of a civil society.
Any atheist can choose from any theistic moral lesson and argue for or against. I personally think the Good Samaritan holds a value. Good human moral reasoning contained in that tale.

Why does a gawd writing rules necessarily make those rules objective?

@Uberdem
Why do you seem to think rape is okay in any worldview? Why did you pick Hitler, why no the popes that called for the crusades of the middle ages? The popes called for mass murder, just as their god commanded and committed. Your god was fine with his followers having young girls as sex slaves. My morales come from me treating people how I want to be treated. Uberdem, why do the religious states of America have the highest divorce rates, and murder? Why do so many christians break their gods commandments?

@Uberdem: First, your society, yours, determined that to stone a woman for being raped was to restore the honor of her husband, father and brothers and wrote it in your Bible, read Leviticus. Your society, yours, ruled that burning people at the stake to tell the truth, or because they were women and healing people with herbs, was to fulfill the law of your god.
Second, there is NO evolutionary theory, evolution is a fact and evolutionary fact isn't even discussed by the Vatican, it's only discussed by ignorant idiots. You are an idiot? (Serious question). And it doesn't matter exactly how it sounds to you. Evolution is NOT a vision, and Hitler was a disgusting racist, like the ultracristian white supremacists, those who advocate teaching creationism in schools.
Third, NO, Larry Arnhart defends social Darwinism, which is a solemn stupidity, as is neoliberalism. The moral basis is biological, moral rules are cultural and as social norms change according to the culture and society we analyze.

NO, you're not getting anything.

A) Good and evil are concepts that change according to the culture and society to which you ask. The moral bases are biological and revolve on three pivots: No murder, no incest and no cannibalism. Although these pivots will vary if circumstances become sufficiently extreme: Killing if it's necessary to survive, or defend the people nearby; incest if extreme isolation occurs; And cannibalism if extreme hunger is suffered. There have even been societies in which, if these extreme circumstances reproduce for long enough time, the violation of these biological moral standards become normal.
B) Moral norms are cultural and not, there are no right and wrong standards, there are human norms of culturally evolved societies and human norms of culturally unevolved societies, eg Canada, Sweden, or Denmark, and United Arab Emirates, Yemen, Sudan And North Korea... I usually do this by differentiating between countries where the death penalty is illegal and those where it still is.

Sorry, dude, god doesn't exist and the bible was written by Greeks in the 3rd century, there're better books written much earlier... and much later, I advise you the Silmarillion.

Ah, and I'm atheist, I don't depend on any religious worldview for absolutely nothing and your god is one more of so many invented.

The Green Lantern Corps bless you.

@Uberdem

You said "God of the Bible has to exist in order for us to account for objective"
Well, that is flat out wrong. First, you have to produce a god, which no one ever has. Second, you have to confirm that the bible is a fact which no one ever has."

You said "1) Atheists say we as a society collectively determine our morals. And that they can sometimes change or evolve. So what happens if the larger majority of our collective society decide tomorrow that rape is morally acceptable because it propagates reproduction and therefore our species will grow and be stronger? Obviously this is hypothetical but I'm saying this to say that your, the atheists explanation is totally arbitrary." Which atheists? Besides Morals are dynamic and created by the society that lives within said morality. I put it to you that the Spartans decided that babies with defects would be cast off of cliffs and to them at that time it was moral. There is nothing arbitrary about society dictating morals. It is simply the fact and the historical record.

You said "2) Atheists always sound like they are evolutionists. But the foundation of the evolutionary theory is that "nature selects the strongest and the weak don't survive" so according to this worldview Hitler was right in trying to exterminate the Jews because he perceived that his race was the strongest and it is therefore his evolutionary prerogative to weed out the weak.
That's the one of the foundational principles of evolution but yet you are not saying that when it comes to morality. Instead you say that nurturing and caring for the weak is how the species survive? Sounds a bit contradictory to me." Again, which atheists? And that is not the basis of evolution not even close. You based your whole argument on a false assumption. Your account about Hitler is also incorrect.

You said "3) Atheists often quote Professor Larry Arnhart, he says that morality is basically social norms :"
Again which atheists. In my opinion (and the facts overwhelmingly back me up) He is right! But alas, That is not what Professor Arnhart said. He said that "ethics is rooted in human nature." cited from 'Darwinian Natural Right' So again you based your argument on a falsehood.
The rest of your post is gibberish. there is no "God's nature". you have to produce a god first. And you can't say that your morality is the right one.
1) Because it isn't right for all people at all times and everywhere. I actually don't think christianity is moral at all. Brainwashing children, in my opinion, is immoral and actually a crime. Genocide, slavery, propagating disease by suppressing knowledge and science are all societal norms of christianity.
2) What gives you the fucking right to say any society is wrong? (rhetorical question no need to answer.) The fact is that morality comes from the society that lives within that society. It changes over time.
Your whole claim is properly and successfully refuted. Like all christian nutcases, you base your arguments on assumptions, the biggest being that there is a god. You never prove shit. You just make wild fucking claims that are unsupported, and incorrect.