Sometimes abstract ideas are hard to communicate. The moral grounding problem, for instance, can be easily misunderstood. When arguing for God's existence, many Christians will point out that God is necessary for objective morals and duties to exist. Since morals and duties are real (torturing babies for the fun of it is truly wrong always), one can therefore conclude that God exists. This argument turns on the concept of moral grounding, that is that in order for values and duties to be considered moral, they must be objective and therefore be anchored in something higher than humanity.
Whenever I have discussed this point, atheists usually misunderstand my position. They will normally respond with "How can you say that atheists are immoral because they don't believe in God? I'm a very moral person and I know all my atheist friends are moral, too." However, I've not claimed that atheists are immoral. I know several atheists who are indeed very moral individuals. So, in order to help clarify the idea of moral grounding, I'd like to use an analogy.
After the Civil War broke out in 1861, the Confederacy was eager to show themselves as an independent government. That means they had to have an elected leader (Jefferson Davis), a representative congress, and they needed to have some form of currency so that the government and its citizens could do business. Thus, they began to print Confederate currency in the same month as the start of the Civil War: April 1861. The Confederacy printed about $1.7 billion in paper bills.1 However, in that time currency was normally understood to be redeemable for some hard asset, like gold or silver.2 Since precious metals were hard to come by, the Confederacy's currency wasn't backed by any hard asset. The notes were basically a promise to pay after the war was completed. Because there was no hard asset to back the currency, it devalued rapidly and by 1864 was considered practically worthless, even though the Confederacy was still in existence.3
Now, I'm sure the Confederate States had some very good economists in their colleges and businesses. They understood finance, trade, and supply and demand. However, their skill as economists mean nothing if they are plying their trade with Confederate bills. It isn't that they cannot recognize value it's that they basis of their currency is not grounded in anything outside their own system. Confederate money wasn't based on gold, which offered an objective and definitive value. It was based on whatever number the Confederate society chose to print on the bill. Because there was no objective standard, the currency became worthless.
Moral principles work the same way. A person can have a very skilled and nuanced understanding of morality and truly be a good moral person, just like our skilled economist or businessman. But if you are trying to say that moral values themselves should be followed, then there must be something beyond the agreement of men saying so. If not, morality collapses into relativism. And as we saw with the Confederate dollar, it can quickly become completely worthless.
2. Bordo, Michael D. "Gold Standard." The Concise Encyclopedia of Economics. http://www.econlib.org/library/Enc/GoldStandard.html Accessed 4/9/2014
3. "Confederate States of America dollar." Wikipedia. http://en.wikipedia.org/wiki/Confederate_States_of_America_currency Accessed 4/9/2014