I noticed that in society, people use mental illness labels such as "psychopath", "autist", "narcissist" or "schizo" to dehumanize individuals and invalidate their thoughts, feelings and opinions on the basis that they are crazy and their philosophies are irrational (For example, a psychopath with narcissistic tendencies may try to preach his philosophy of egoism to others and people automatically label him first and assume he has nothing useful to offer)
But mental illness is a subjective concept, right? Mental illness is esentially just a sign of someone's brain-functioning and behaviour deviating from the general pattern of someone "normal". When someone goes to get diagnosed for a mental illness they are "not mentally ill" when they enter the room and "mentally ill" when they leave, so we don't actually know if anyone is mentally ill based on a subjective criteria (Greg might have just been a sad guy before he went to the doctor but now he has clinical depression). And mental illness is also hard to diagnose based off of deception as well. The psychopaths who are diagnosed are usually low-functioning ones but the high-functioning ones are skillful enough to hide it and therefore don't get diagnosed. And thus the image of a psychopath is associated with the low-functioning version, one who is emotionally unstable and impulsive because they are the ones who get caught, I'm sure if we knew what their motives were, many CEOs would be considered severely mentally ill as well. And each individual might see individual behaviours as crazy even though they are not officially mentally ill.
So would these peoples' philosophies still be accepted as valid philosophies by the philosophy community or would they be rejected on the basis that they can't think properly? After all, certain philosophies align with some of these mental illnesses, egoism, for example, aligns with a psychopath's instinct to preserve himself over others. Or a narcissist may hold the philosophy that the self has infinite potential. Or someone with autism may believe that humans have the same intrinsic value as all other objects (materialism?) due to lack of cognitive/affective empathy. Or someone with clinical depression may follow a pessimistic version of nihilism. Where do we draw the line?