Truth blinds. It really is as simple as that.
Sadly, in order to prop up Truth, True-Believers need to redefine things to make them meaningless in any context other than within the context of their Truth. The gentler, kinder human qualities are not such unless one is being gentler or kinder in the service of that Truth, or (as the religious) like to put it, through God. The non-believer can site examples until blue in the face of being kinder and gentler, but for the True-Believer, they simply don't count as examples, because they are not through whichever Truth they hold dear. In this way everything revolves around this or that miscellaneous, anonymous Truth and nothing else can ever have any merit of its own.
Since Truth is absolute for the True-Believer, Morality must also be absolute or it ceases to have meaning for the True-Believer. Ordinary human considerations simply do not enter into the discussion, because humans are irrelevant to the Truth. To tell them a non-believer is moral is a contradiction in terms for them. They simply cannot reconcile the ideas.
Plumjam is actually quite correct about Atheism (and one could include skepticism in this) not being "moral," in that it does not take as its first cause God qua moral Truth. But this is child-think, a desire to stay under Daddy's protection and for Daddy to have all the answers for you. When one grows up, intellectually and emotionally, one must discard such child-think in favour of more sophisticated way of thinking and being - one must develop one's own reasons for being moral.
Now atheim itself (and the same is the case with skepticism) does not prescribe a moral way of being or a moral course of action. In Plumjam's perception, theism does and therefore is a positively moral "direction." Now arguments many and various have been presented about what where the moral compass actually points, and with good reason. The direction is deliberately ambiguous - and most frequently, quite contradictory. The net result is that the moral compass points in all directions and no directions at once - effectively being the worst of all possible cases.
Nevertheless, this is not to say that atheism/skepticism precludes morality - it merely requires a more sophisticated idea of what morality is and what it means to be moral. Gone is the absolute authority, gone is simple obedience as sufficient condition to being moral. More is required, not the least of which is the effort to develop an adult way of thinking. Accepting responsibility for one's attitudes (not just one's actions, one's attitudes) is not an easy path, and for many, it seems, it is not one that they choose to even attempt. Nevertheless, it is a necessary step in the growth of the individual.
Typically, religious moralists will level the charge at atheists and other "moral nihilists" that we don't think it is Wrong kill, and in their strange Truth-based sense of the word wrong, they are correct. However, at no time does the atheist/moral nihilist think they are Right to perform immoral actions. This cannot be stressed enough. Consider a moment what it means for someone to be absolutely confident that what they are doing is intrinsically, objectively Right. And since their moral "source" is ambiguous and self-contradictory, anything can be perceived of as Right. This explains a great many many things in religion's sordid history. There was, of course, no checks on this rabid mentality because the millennia long witch hunt to eradicate skeptical thought had been won and most of the unbelievers were dead. Absolute power, as they say....
Where does this leave the atheist/moral nihilist? It leaves one looking elsewhere else for one's guide for moral thinking. Some, to be sure, will simply discard the idea as irrelevant and adopt a purely self-serving attitude, but usually that arises from placing too much import on the idea of morality needing to have an objective, absolute "source." More typically, as has been clearly expressed in this thread, when one rejects the idea of absolute morality, one also loses the need for Truth to conceive of morality or of being a moral person. A more sophisticated, adult approach is developed. The definition becomes a more natural, less contrived one, focussed on others (since morality needs a context), rather than on some vague, indefensible Truth. We perceive of our actions as moral or immoral based upon what they are, their effects on ourselves and others, and whether they are in accordance with the reasonable expectations of ourselves and those around us. An action ceases to have some property "moral" or "immoral" supervened on it, the idea of which quickly reveals itself to be indefensible. Morality becomes human-based cooperative venture, as universalizable as we choose to make it, but never absolute. The benefit for eschewing absolute morality is adaptability - something some condom-hating and HPV innoculation-hating fanatics could use a heaping helping of.
This also has the advantage of causing one to look outwards for one's "source" of morality, just as verificationists look outward for verification of theirs and others' claims. And this is the counterbalance that the True-Believer does not see at work in the atheist/skeptic. We do not perceive of ourselves as absolute moral authorities. This is difficult to explain to people intellectually and emotionally poisoned by the idea of individual conscience - who perceive of themselves as absolute moral authorities. Even those who do not rely on individual conscience, rely on a body of work that has no consistent prescriptive content except accept the Truth and define all things in terms of it.
. My upbringing was irreligious, and we're doing very well out of it.
