First off, your example wouldn't even be illegal, as far as I know: at least in the US, fashion is not covered by copyright.
Secondly, I don't see why it would be immoral: the designer of the dress is not hurt at all by your copying it. Now, if you claim your dress has actually been made by said designer--e.g. you infringe on his trademark--that's basically fraud and a completely different case.
The real issue is that it seems you define "wrong" as an enumeration of things you shouldn't do, among which you seem to include copying without permission.
You haven't given any reason for it to be wrong. I think that something is not "wrong" or "immoral" by default; unless there's a good reason for something to be wrong, it shouldn't be. And, as copying like this does not obviously harm society, I see no reason for it to be wrong.
"Wrongness" seems fairly straightforward in this context: you're deriving utility from the work of others without the recompense that we as a society have deemed is their right to extract.
The major content producers and their organizations (the RIAA, etc.) are stupid, but I think it's rather hard to allege that they don't have the moral high ground.
Secondly, I don't see why it would be immoral: the designer of the dress is not hurt at all by your copying it. Now, if you claim your dress has actually been made by said designer--e.g. you infringe on his trademark--that's basically fraud and a completely different case.
The real issue is that it seems you define "wrong" as an enumeration of things you shouldn't do, among which you seem to include copying without permission.
You haven't given any reason for it to be wrong. I think that something is not "wrong" or "immoral" by default; unless there's a good reason for something to be wrong, it shouldn't be. And, as copying like this does not obviously harm society, I see no reason for it to be wrong.