Why is it that the term "synthetic drugs" bugs you? From a chemistry perspective, I don't think "synthetic" is really meaningless. In the context of drugs I have always taken it to refer to drugs that have been synthesised from precursors through a series of chemical reactions rather than one that is a natural product or extracted from a natural product without modification. As such, there will be different concerns regarding the quality of the manufacturing process (e.g. has it been purified properly to remove unreacted precursors and solvents and dose issues become harder to manage the more concentrated the product).