Why are perfect clones sick, bad and wrong? Why is identity such a muddled issue? Simple: exploring it just raises too many questions.
"It's hard to think about, so it's bad"? That's...well...that's a loser attitude, bluntly.
Or, put it another way: perfect clones, being completely impossible (unless we in our technological progress somehow become gods, which I find incredibly unlikely), raise issues about identity that can't be solved with any available knowledge and can't be tested with any future knowledge, and the presence of such an unsolvable problem makes people either jump to certain conclusions rooted in personal beliefs or become slightly uncomfortable and ignore the issue entirely (in this respect, it is very much like subtracting infinity from infinity). So one begins to run in circles when the issue is approached from a theoretical perspective. No amount of arguing is going to provide any sort of clarity, since the question itself has no answer.
That's philosophy for you. And, well, identity is a philosophical issue more than anything. (Until we get laws on the subject, but that doesn't matter much for our current discussion.)
Observe how identity is a question of belief. This is because human identity itself is something we perceive axiomatically and possess no real knowledge of.
I'm reminded of something I read about...Eucleid? Some early mathematician tried to find a bunch of axioms from which one could define the rest of geometry, and came up with five. The first four were simple, but the fifth was...complex. Eventually, though, someone used the first four to derive the fifth.
Why shouldn't these other things, identity and such, be similar? Shouldn't we at least try to see if we can derive these important things from more basic things?
Attempting to provide the concept of "you" or "me" a definition is doomed to fail, since these are the concepts you build definitions upon. To deconstruct them, you must deconstruct standard human thought first.
So?
EDIT: In a move that's a little more down-to-earth, a question to both sides of this exercise in holism vs. reductionism: can you consider your identical twin brother to be "you"? Why?
No. His experiences and personality are different. More relevant to the clone thing: Identity isn't started at birth. You can't talk about the self-image of a newborn. There's no specific time that a self-image and personality forms; I'd say it forms slowly over the first years of a child's life. It's a fuzzy area, not a "line" through time like adults' identities can be described as. You could argue that everyone starts at the same point, but not only would this be irrelevant, it would be wrong--people born in different hospitals, or even different rooms in the same hospital, or even the same room at sufficiently different times, have different experiences.
