My initial, poorly fleshed-out question was a measured response to your initial, poorly fleshed-out question. I was giving your question the response it deserved. If you wanted a more thoughtful response, you probably should've gone with something a bit more thoughtful than:

  "I don't believe in objective morality."

  "HA! WHAT ABOUT MURDER?! GOTCHA!"

What about murder? Explain, please. What about murder do you think so beautifully proves objective morality that you don't need to do anything except mention it? If anyone is trolling, if the burden of proof is on anyone, it's you. At the risk of "putting words in your mouth", you seem to be claiming that there is an objective morality. I am saying "I see no evidence to support that claim, and therefore reject it". My rejection does not then require evidence to support it.

If you really want me to spell it my thinking for you: I have no reason to believe in an objective morality, because the only things I think are objective in this universe are related to physical laws of nature, which happened by random chance. From there, I see no reason to link these physical and random laws with our human understanding of morality. If there was a prime mover that created these physical laws and ordered the universe, and was therefore "above" my conception of the universe, presumably any moral code this prime mover laid down would be "objective". However, I do not believe in such a being.

If you have a logical argument for objective morality without a higher power, lay it on me. But "what about murder?" is not an argument. I feel like I'm beating a dead horse here, but just to be clear: plenty of people and cultures have felt morally comfortable with what you probably think of as murder. Please stop wasting our time if that's all you have.