In the aftermath of the Aurora, Colorado massacre one of the things we've learned is how a number of young men shielded their girlfriends from the bullets with their own bodies, some of them dying in the process.
These wonderful and amazing acts of altruistic heroism raise a question. On naturalism (atheism) what sense does it make to give up your life to save someone else's, particularly someone to whom you bear no genetic kinship? If the whole purpose in life is to produce offspring and pass one's genes into future generations then it seems that, on atheism, the morally correct thing would have been for these men to have hidden behind their girlfriends and let them take the bullets.
In other words, the atheist has no basis for saying that what these men did was "good" or admirable. The atheist, of course, can be glad there are altruistic heroes in society since he may one day benefit from another's selflessness, but if someone were to have acted selfishly in that situation by hiding behind his girlfriend, the atheist would have no basis for saying that that would be in any way a bad or wrong thing to do.
What most people consider noble, the atheist has no grounds for thinking noble at all and considerable grounds for thinking foolish, yet I'm sure most atheists do think the actions of these men in that theater were noble. That's why it's so difficult to live consistently as an atheist.