I think the author and those he quotes may be confusing cause and effect here. People are prescribed the psychoactive drugs precisely because they do have mental issues. If they act out on the mental issues, it is not because of the drugs—it is because the preexisting mental issues are not adequately controlled.
It’s kind of like observing that a disproportionate number of obese people drink diet soda, and then concluding that diet soda causes obesity.
That said, I do not like the propensity to prescribe drugs without first addressing the behavioral issues. Behavior therapy has some success in treating certain mental disorders. (Some mental illnesses, like schizophrenia, cannot be treated without drugs, though.)
I agree with you. However, there are some interesting associations(which is not causation.)