If your defense is “I’m fundamentally unable to distinguish acceptable and unacceptable behavior, to the level of random physical violence, in a way that most people are not,” then you are saying “I am not fit to be in society,” and the only thing society should say back is “yes.” It’s insane that “incompetent to stand trial” does not lead to automatic lifelong committal in more sympathetic cases, and execution in those that are less so.