Acim, the Bible tends to lend itself more toward emotional catalysts -- emotional foundations to build their so-called morals. FEAR is an emotion the Bible draws upon on a very frequent basis. "Murder is bad," being one of the most fundamental. I'm not sure if you asked this question and all people gave you were emotional responses or whatever, but you still desire hard evidence. Well, in this case, so does every atheist from a theist. The party that posits a truth therefore bears the burden of proof. But hey, beggars can't be choosers. Therefore, I'll play Devil's advocate, ironically enough, for the time being.
"Seems that non emotional responses are hard to come by." - Acim. You said this based on one forum on one corner of the vast internet and assume a NON response is definite. Perhaps not, you did ask again, but still...this is a small forum (and I am new.) I'll offer you a response though, however, it will be void of hard evidence, since you'll find it fairly difficult to materialize HARD evidence when it comes to matters of morality. Just as we atheists find it difficult for believers to provide hard evidence themselves...
Why is murder bad? Our species is the first on this planet to develop consciousness. As a by-product, self-consciousness. We are aware of our mortality -- the first to be so. We are aware of time. So much so, that we've defined it and even measured it. Without the Bible, I can tell you I've developed and nurtured empathy and sympathy. The hardships I come across, I don't wish upon others, though I realize it is a necessary evil to learn and grow from our own mistakes. And when you consider, from the atheist's point of view, just how INFINITELY rare life, much less consciousness, is, the 65-some-odd years the average American lives on this slowly rotating planet is all the more precious. During those years -- those incredibly few and valuable years, we learn to love, hate, provide, respect, and grow as individuals and as a species. We have families who rely on us. Or not. We have fans who adore us...or not. Life is what we make of it, and each is inherently as necessary as the next. Each can play, potentially, an important role in the growth of our species. Take that knowledge, and then introduce the concept of murder, and you'll find your "hard evidence" for morality sans religion and sans emotion...whatever that means.
Not everyone will feel the way I do. Some take no guilt from the killing of another life. If you ask me, they forfeit their own right to live. But, as an atheist, murder breaks the bonds of emotion. Life is precious. It's a right, as far as I'm concerned. Though sympathy and empathy are emotion-based, it should, in no way, distract from the obviousness of the cruelty of murder. Emotion aside, life is precious, and we all deserve the chance, sometimes chances, to improve ourselves and our species. Those who seek to end life...are bad. Simple as that.