Please demonstrate which is invalid in what fashion.
In this case, the car thief may well violate your morality, but in so doing, he would satisfy his own morality.
It is not "my" morality, it is morality. The reasoning is applicable to every person.
The prickly problem is that you're claiming a superior morality -- but on what basis? Are your "wants" somehow better than his? Not according to you: "Neither I nor any other human is more inherently valuable than others." So your wants are not superior to his -- nor, by extension, is your want-based morality superior to his. So he can steal if he wants, and you can not steal, as suits your assessment of the situation. And thus we reach a situation where the same underlying moral basis, "what I want," leads to opposing views of "moral behavior." In other words, your morality has no rational meaning.
Nope, sorry, try again. You might try looking at the premises and pointing out which is wrong.
I did. I slapped you across the face with the cold, wet fish of reality.
Really? Looks like the cold, wet fish of your confused misinterpretation to me.
I demonstrated that basing moral reasoning on "what I want" can lead to contradictory moral judgments. What more demonstration do you need?
It is not "my" morality, it is morality.
So you're claiming an absolute morality, based on "what you want" and an assumption about "what others want."
The reasoning is applicable to every person.
The problem is, so is my reasoning applicable to every person -- and it leads to the opposing conclusions -- and thus to the conclusion that "want-based" morality is inherently contradictory.
Look, FRiend, it is not enough simply to claim "it is morality." You've got to be able to defend the claim. What GregF and I are doing, is challenging you to provide the objective basis by which you can stoutly claim, "it is morality." And so far, you've failed to do so.
I do not wish to be harmed. This is universally true. Even a masochist has multitudes of types of harm he would object to. This premise is unassailable.
But it's also incomplete, which is why it's not a valid premise for the type of universal moral principles you're claiming to demonstrate.
For example, I am willing to risk being harmed in cases where I believe the probability of gain outweighs the potential costs. In some cases I am willing to actually be harmed, for the same reason. If I perceive that the risk of being harmed by stealing your car is outweighed by the benefits of my taking it ... your "morality" does not address that.
We could also attack the premise from another direction: what "harm" is it to you, if I take "your" car? What makes it "yours" in the first place? What confers any sort of moral weight to the word "your?" At the moment, the only thing that gives the word any moral weight, is that you don't "want" to lose "your" car -- it's "yours" because you "want" it. But I want it, too ... so doesn't that make it "my" car?
It might just be the case that I don't care what you want as much as I care about what I want, with minimal cost to myself. We might summarize this alternative moral system as, "whatever I can get away with." (Perhaps we can call it "Clintonian morality.")
From this it follows I should not harm other people. You already admitted this conclusion is logical supposing the premises are accurate.
There are several problems here. First, I did not suppose the premises are accurate. Second, your first two premises do logically imply the third premise. In fact, they lead more naturally to a contradiction of your third premise.
Let's accept that you do not wish to be harmed, and let's accept that you're no more valuable than anybody else, which in this context means that your wants are no better than mine. The second premise says that I don't have to consider your wants, because they're no better than mine -- if what I want harms you, there's no moral problem, because our wants have equal value. There is no reason why I should not behave as I want to, regardless of whether or not you're harmed.
What you're presupposing -- and again, this is the problem -- is that some wants are superior to others. Specifically, that your desire not to be harmed, is more important than my desire to get what I want.