The insanity of the insanity defense

Anyone who murders someone, when it is not in self-defense, is insane. Therefore, if you accept the premise that some murderers shouldn’t be prosecuted because of insanity, then we might as well invalidate all the murder laws and just send all the murderers to psychiatric hospitals, where they’ll get red-carpet treatment (at the taxpayers’ expense) and eventually be released back into society when some quack psychiatrist deems them “rehabilitated.”