A while back, I ended up trying to think of some little meme-worthy slogans about morality. One that came to mind was something along the lines of "If morality is objective, it's random."
The rationale behind it is essentially this: I think morality is more or less "technically relative": It's based on our instinctive needs and desires. Presumably we all want to live, therefore we outlaw murder. Essentially, we can deduce general principles to use to maximize everyone's satisfaction in life. It's messy at points, but it's fairly firm. Much more so than the typical fundie's morality.
Objective morality, well, if there's a "Don't murder" objective moral law out there... How do we find it? If magic men in the sky are supposed to tell us, how did they figure out that law? If the magic men define it, well, what gives them the ability to do so? What's the basis behind the existence behind these laws? Are they completely baseless?