When I was in college, there was a street person who would periodically wander in to our dorm. He was basically harmless, so nobody bothered him, we being enlightened college students and all. He would sit in our lounge and play this same maudlin Peter, Paul and Mary song over, and over, and over, for hours on end. Eventually, people got sick of hearing that song and him hogging the stereo, and a group of guys would invite him to leave. And he would launch into a tirade, including the deadly threat "Jack Kerouac is a friend of mine, and I'm gonna tell Jack Kerouac about you guys, and he's gonna write in his next book that you guys are not cool!"
Yes, he actually used the words "not cool." Nobody can make stuff like this up.
I think of this character every time I see someone announce pompously that there are no moral absolutes, and then, in the very next breath announce that it's "immoral" for society not to allow gay marriage, or universal health care, or free housing, or for us to invade Iraq. I want to ask "suppose the people who oppose you, instead of offering moral arguments, simply say 'screw you and the horse you rode in on. We completely reject your moral arguments as worthless and we're not going to pay the slightest attention to them.' What are you going to do? Tell Jack Kerouac on them?" Because, seriously, you can't appeal to a higher authority because you don't believe one exists. You can't appeal to power because you don't have any. You're trying to change things, remember? And the people who disagree with you refuse to change. So what are you packing? You will call them immoral? Whoa. Heart racing ... head pounding .... gotta sit down .... hyperventilating ... okay, better now. You have nothing. Your claim that your opponents are immoral packs all the wallop of that street guy threatening to tell Jack Kerouac on us.
But the Constitution guarantees everyone the right to life, liberty and the pursuit of happiness. Well, actually, that's the Declaration of Independence, and you get an honorary Tea Party sticker for ignorance of our founding documents. Plus the Declaration of Independence claims that all men have those rights because they are "Endowed by their Creator." So presumably those rights have been nullified by separation of Church and State. Talk about your Law of Unintended Consequences, although, if you don't believe in a Creator, you can't logically argue those rights anyway. And "Endowed by their Creator" is the only theory of rights in any of our founding documents.
Okay, but the Fourteenth Amendment guarantees equal rights and due process, and if we elect a liberal Congress, we'll get those reforms, and if we appoint a solid majority on the Supreme Court then those rights will be secure. Until your opponents get back in power, and change the balance of the Supreme Court, and repeal your laws, and amend the Constitution. But that will be immoral! Except they won't care in the slightest what you think, and then what are you going to do? Anything enshrined in the law can be repealed. In fact, the fury evident in posts to Daily Kos, Crooks and Liars and Huffington Post reeks of impotence, of rage at being angry and being totally ignored by the opposition. "Hello, Jack? It's me. They're not being cool again."
The mere fact that your opponents debate you at all is due to three things. First, you appeal to ideas they consider morally grounded. Second, they feel some moral obligation to support their ideas. In other words, your opponents are moral. But third, and most dangerous to your case, they don't realize how empty moral claims are if they're backed with nothing besides personal feelings.
I occasionally wade into some debate on a lightning rod topic like gay rights and ask "Okay, gay marriage is a right. Prove it." I get a ton of wharrgarrbl, heavy on the caps and exclamation points, lots of vitriolic rhetoric, but precious little in the way of rational discourse. The few reputable folks who do try to present a coherent argument fall back on things like social consensus and thinkers like Voltaire and Bertrand Russell. The latter are the easiest to deal with, since those are arguments from authority, pure and simple. Okay, Voltaire agrees with you. Prove that he's right. Social consensus is a little more robust, but what if the consensus changes? After all, the consensus not very long ago was that blacks were inferior to whites, and it wouldn't take much to shift back to that paradigm (it's becoming ominously obvious that many people still hold it). And if social consensus is the arbiter, what gives you the right to try to change it, especially by force?
How, ultimately, can you prove your opposition to slavery is on a different plane from not liking broccoli? What gives you the right to speak about right and wrong as if your values carry any weight outside your own skull? If you talk to people in prison (I have), many of them simply don't see why the things they do are illegal. You have it, I want it, so if I can take it I will. Do you have anything other than "don't take my stuff" or "don't rape my loved ones" as a counter argument? There seem to be only two possibilities, and if you can think of more, let us know. Either moral ideas reflect a reality that exists independent of our perceptions and desires, or they're purely personal preferences and nothing more. Appealing to group consensus or the spirit of the age merely means replacing individual preferences with group preferences or the preferences of some particular time.
And if people with a radically different consensus come along and replace the consensus with something you find abhorrent, what are you gonna do, tell Jack Kerouac on them?