It is an obsession.
I can't count the number of FReepers I've seen post about how much more moral they are than any number of religious people you can put in one group. As if that's proof that atheism is somehow superior to faith.
What they fail to consider is that they're riding the coattails of a very strong Judeo-Christian ethic and still enjoying the benefits of it.
Some decades down the road when that ceases to be the case, we'll see what atheism without Christian influence can produce. Oh, wait a minute,... something about China just popped into my head, and Pol Pot, and Lenin, and Stalin, and.....
The really important issue--the root of the whole matter--is that morality is in its very essence submission to the will of the Creator. No matter how good or altruistic atheists may be they do their good deeds because they want to and not out of obedience to G-d, which means it isn't morality at all.
Once "one can be moral without G-d" is translated as "one can submit to G-d without G-d" then it is shown for the nonsense it is.