Let us suppose that one certain villain's motives and actions can be mostly explained by a particular medical condition or other misfortune. Consider a tyrant who commits atrocities due to mental instability at the onset of paranoia, etc.: the condition itself is the cause, not their intentional exploitation, or the natural result of mistreatment by others.
Unfortunately, any discussions on this issue I found online always seem to end up suggesting adding a token foil character with similar conditions to contrast the villain, or avoiding the practice altogether. And on my side, although considerable effort has been made in researching medical references to ensure logical consistency and accuracy, I am aware of the following two possible controversies:
- The condition can be viewed as a way to excuse and even justify the wrongdoing of the villain;
- Conversely, this can be seen as an unfair accusation that stigmatizes the group in question by suggesting that the condition is solely responsible for creating evil.
What else can be done to minimize these two negative influences as much as possible?
If I may elaborate on my intent in asking this question, I want my fiction to be believable more than reader-friendly. I am not against but rather in favor of the use of tropes, including stereotypes, but only when they are substantiated by sufficient factual research and logical consideration. Being called factually inaccurate is much, much more hurtful to me than being accused of insensitivity.
To give more context, the fiction in question involves an attempt to examine the basis of morality (reason vs. emotion) and whether moral responsibility derives from free will. This villain protagonist of the Mad Scientist archetype with SzPD and/or ASD does fit the stereotypes of apathetic (coldness, detachment), unfeeling (alexithymia; lack of empathy), and amoral (insensitivity to social norms; "moral unevenness") very well, but would later take a step up in moral responsibility through character development. I am working to make sure these stereotypes do have clinical evidence support, and, when I have done my due research, the last thing I want is to be criticized for "misinterpretation."
So, to append a new question here: How can I avoid conveying the wrong message when establishing a character with "boring stereotypes" of some mental illness, negative experiences, etc., that are actually factually and logically self-consistent?