Perhaps "claiming morality" is too thin a line to stand on. I aspire to the ideals of honor and integrity, both to my self and others. I make no claim to have either, for those are just words if they cannot be backed by evidence. However, those are the two major ideals in my life, and while I fail at times to adequately exemplify those ideals, there are times when I feel I live up to them. You may ask me to define my perception of honor and integrity, and I'd be hard pressed to do so without writing a small book. But to summarize, I try to treat others as I would like to be treated. The Golden Rule. I don't want people killing or raping me, therefore I don't kill or rape people. It seems like it would not be something I would really appreciate. I like the things that I own, and wouldn't deprive someone else of their belongings, even if for a good purpose. (Like taking church-goers Sunday clothes and giving them to the homeless.) I define "bad" as something I would consider a misfortune if it happened to me, even though like everything else there are exceptions where I could see the "good" in something "bad."
People, it's not rocket science. Atheists may be godless, but we're not hollow shells. I am the product of all that has happened to me, all that I have learned, and that which my parents have taught me.
But, it you are right, it doesn't matter in the end. If it does, please feel free to say why.