What an novel approach to youtube commenting- posting a link to a thread on a forum somewhere else. Let's give it a spin though eh?
I've never heard of an atheist, or even a group of atheists, saying that they and they alone have the ability or right to decide what is moral action for entire societies. Rather, what comes up frequently is the call by atheists that morality should be decided secularly and rationally. "Coveting thy neighbor's wife" isn't considered an immoral action because the bible says so, but because its effects (unwanted attention, fixation, paranoia, jealousy) are considered by most people to be negative. The secular approach to morality is that actions should be judged on how they affect human health and happiness. Murder, theft, violence and rape, are all very negative things for the victim, and so any population that desires maximum health and happiness will take steps to guard against them by defining such actions as immoral. The thing that makes us think this way is not god, it is empathy, or the ability to predict and internalize the emotions of other people.
Moral authority doesn't intrinsically come from government. The function of government is to add stability to society, be it caring for the less fortunate, organizing for military defense, distributing resources, or upholding laws. People give powers to their governments for specific purposes through laws, in this case, so that acts deemed immoral by the citizens can be investigated and if necessary punished from an impartial distance. A majority of people do not want to be murdered, and believe that murder is immoral, so governments are empowered with the authority to investigate murders and punish people who are found guilty. The role of government in morality is to enforce it, not define it. The alternative to empowering a government through law is mob justice, which will frequently arrive at incorrect or excessive punishments due to the emotional investment of those involved.
Some personal freedoms must be surrendered to be accepted into, and be supported by, a government. Drafting doesn't exist purely to inconvenience people, it exists because it is recognized that having a capable and ready military is one of the best ways to discourage destruction and social upset from people that seek power through violence. We also agree that taxes are fair and reasonable, and pay taxes to our governments so that we can benefit from actions it takes on our behalf like maintaining educational and health programs. Money is nice to have as an individual, but we recognize the fact that we are happier and healthier when some sacrifices are made for the group as a whole.
As far as the examples provided of "difficult" moral questions
....in drunk driving, the issue is one of risk. Drunk driving is easily demonstrable to be a dangerous activity with VERY high likelihood of damage to people and property. Just because no damage has resulted in a specific case doesn't matter when the danger has been proven in many prior occasions. Morality can include acting preemptively in situations where no actual harm has yet been done due to our ability to learn and predict consequences. Teaching children about the danger of firearms and locking firearms away from them, even though it deprives them of the freedom to accidentally shoot themselves or other people, would be considered by most to be a morally correct action because it is far the less harmful of two potential outcomes. (That said, if you have assessed the risks and make a deliberate decision to commit suicide with a car and a case of beer, the moral complications completely disappear if you do it where you can't cause damage to other people and their property).
... societies and governments can be objectively immoral but only so far as they harm health and happiness of their individuals. One society's fondness for the taste of cat meat, and its subsequent legality at the state level, doesn't make them immoral no matter how much their neighbors might blanch at the idea. On the other hand, North Korea is a rare example of an objectively immoral government. One that brainwashes its people, prevents free access to information, even prevents people from leaving, to the point that it is now a nation consisting mostly of poorly educated malnourished paupers. Everything that can be done to diminish health and happiness, short of just executing everybody, is being done there.
Secular morality is built on the empathy to recognize happiness and suffering in other people and the predictive ability to know when to act to prevent or reduce suffering by choosing to the best of our knowledge the least harmful option available. No omniscient, omnipotent entity living outside of spacetime and causality and communicating to our "heart" (I think you meant brain) via untraceable telepathy is required.
