HuffPo mangles moral philosophy to argue against atheism

The Huffington Post has an article by Pastor Rick Henderson titled Why There Is No Such Thing as a Good Atheist in which he makes a superficially coherent argument that given naturalism, the default assumption of atheism, it is impossible for atheists to have objective morals and stay consistent to their world view

"Every expression of atheism necessitates at least three additional affirmations: 1. The universe is purely material. It is strictly natural, and there is no such thing as the supernatural (e.g., gods or spiritual forces). 2. The universe is scientific. It is observable, knowable and governed strictly by the laws of physics. 3. The universe is impersonal. It does not a have consciousness or a will, nor is it guided by a consciousness or a will. Denial of any one of those three affirmations will strike a mortal blow to atheism. Anything and everything that happens in such a universe is meaningless. A tree falls. A young girl is rescued from sexual slavery. A dog barks. A man is killed for not espousing the national religion. These are all actions that can be known and explained but never given any meaning or value. "

This is all true as far as it goes but is also question begging. Henderson is assuming that only an external conscious agent can give meaning to events and also that meaning requires objectivity, neither of which is self-evident.

"A good atheist -- that is, a consistent atheist -- recognizes this dilemma. His only reasonable conclusion is to reject objective meaning and morality. Thus, calling him "good" in the moral sense is nonsensical."

Again the conclusion is already in the premise that to be morally good requires moral objectivity and moral realism. He’s also equivocating as he is allowing “good” to serve as “consistent” and also “moral” which is how he arrives at his contention that there are no good atheists, either an atheist is moral (by objective standards) and therefor is not really an atheist or is consistent in which case not objectively moral.
O.K! In the first place it is true that many atheists live as if morality is objective, even if we know philosophically that it isn’t. Henderson correctly points out that one argument for the existence of our moral sense is evolutionary but denies this confers moral objectivity, which of course it doesn’t, but it doesn’t have to. Most atheists also behave as if they have free will despite there being good philosophical reasons and increasing neurophysiological evidence to suggest we don’t. But evolution doesn’t work that way; our sense of agency and our sense of moral objectivity are probably innate as stopping to philosophise about either would have no survival advantage in the environments where they evolved. It is not being a bad atheist to appear to hold objective moral values.
Secondly, “meaning” is a human construct. It is incoherent to talk about the meaning of events without a conscious meaning making observer but there is no reason why that observer has to be an omnipotent creator god. The benchmark for moral objectivity is as true for gods as it is for us as the Euthyphro dilemma points out. If gods are responsible for morality the subjectivism is theirs not ours but still says nothing about moral realism. We are perfectly entitled to be the arbiters of meaning since, as far as we know, we are the only entity that finds things meaningful. If we ever meet another meaning making sentient species no doubt we will have to negotiate
Thirdly, moral subjectivity does not entail moral relativism as Henderson contends.

[assuming]"…morality was developed to ensure the success of societies, which are necessary for human survival and thriving. Like the rules of a board game, morality is contrived to bring us together for productivity and happiness. If this were true, there is nothing to which we can appeal when we find the behavior of other societies repugnant and reprehensible. Because morality is the construct of a social group, it cannot extend further than a society's borders or endure longer than a society's existence."

“Society’s borders” are porous and flexible. Just as we would have to negotiate with an alien species, should we encounter one, we must also negotiate with neighboring cultures. Even if the moral basis of a behavior is subjective outcomes aren’t, which is why utilitarianism is the go to meta-ethic of choice for resolving these conflicts. In fact the only situation where ethical dilemmas cannot be approached this way is when the contentious behavior is religiously motivated.
Lastly, at least for the purposes of this post, the other bit of question begging in Henderson’s argument implies theism fares better than atheism in this respect. But the religious are just as subjective as they have to explain why the moral examples in their scriptures are correct, especially in circumstances where they patently aren’t. The Bible for instance condones rape, genocide, stoning, slavery, polygamy, and infanticide to name a few which would not pass most people's moral intuition. In fact a holy scripture that was morally consistent for all people at all times and under all circumstances would be the strongest physical evidence that such a religion was true, which is probably why there isn’t one.