Let me break this down for you in how I see this discussion:
Dude 1: "He totally just killed all those people because of the psychotropic medications he was on."
Dude 2: "You don't think that he killed those people because he's schizophrenic and thus, bat crap crazy and heard the voice of God tell him to do so?"
Dude 1: "No way, schizophrenia doesn't cause you to do crazy things! Drugs make you do crazy things!"
You WANT the brain chemistry changed in these people because they're off their rocker. To be real honest man, this starts to become the same discussion as any other science denier (read as: climate change deniers).