Research suggests that their is a genetic cause to AD[H]D. Research also shows certain chemical characteristics which are common to those diagnosed with ADHD but not common to the population as a whole. This suggests that chemistry does play a part in those diagnosed with ADHD.
However, whether there is a biological, environmental, or made-up cause to ADHD symptoms is irrelevant to this discussion. What matters is that these medicines work, and they have been shown to do that in an overwhelming number of cases. With that being true, I don't see why you guys oppose ADD medication.