This is addressing a post of the same title at evangelical Christian Tom Gilson's blog, "The Thinking Christian". Some might think his blog title is an oxymoron but I was willing to give him the benefit of the doubt. I do note it is not called the Ethical Christian...
In his post he is addressing a humanist, who calls himself a humanist but Gilson claims this is "disingenuous". Why? Well Gilson makes a number of assertions, which is he claims atheism entails. There is no point defending or analysing that list because his assertions are blatantly false. Have a look. So as far as I can see it Gilson who is being disingenuous.
What I mean is that for each of these points it is certain that some do hold these position, you might agree with some of them, although very unlikely would disagree with how these are stated and likely have a counter-balancing positive answer or statement of the same. However you would also disagree with some too - since I am not you I have no idea which you do agree with and which you do not. There are certainly quite a few atheists who would agree with none, however worded. So it simply cannot be construed that just knowing one is an atheist gives one any clue as to what positions they do hold in Gilson's list.
Gilson's conclusion of what “atheism” entails is quite erroneous, if this does not reflect prejudice on his part, at the very least, it is a dangerous form of argument. Criticising someone for a worldview of one's own construction that one has involuntarily assigned to someone based on their position on one issue, from which is grossly insufficient to draw any other such conclusion, is prejudice. And this is the basis for bigotry which is ironic given this was triggered by another post, in which Gilson was trying to justify God commanding genocide. As is well known, the first step to genocide is promoting prejudice and bigotry. One important way to help avoid future genocide is to condemn bigotry and prejudice wherever you see it. This condemnation certainly applies to Gilson and through his post he makes a mockery of his claim to know what objective morality is. It is not good enough to assert your morality is objective, you have to demonstrate it and you have failed, thereby invalidating your claim.
Postscript: Actually Gilson's list is not remotely plausible, it is full of silly, pointless, erroneous and idiotic points. It does not warrant any explicit criticism but for somee analysis seethe Barefoot Bum's The Thinking Fucktard