LIFE wrote:So...
Golden"Treat others as you would like to be treated."
What if I derive pleasure from pain?
So? What if others derive pleasure from pain? You test it and if it does not work, then you are out of luck so to say.
LIFE wrote:Silver"Do not treat others in ways you would not like to be treated".
What if Charles Manson was responsible for the death of my family and suddenly stood in front of me?
So? Again, how would you like to be treated if you were responsible for deaths? Though in the situation you describe I'd doubt you do much thinking or care about whats moral and whatnot. But maybe not, maybe you are one of those who do not let emotions to cloud their judgment I dunno.
Is there any ethical code that is practicable at the most fundamental level?
No offense but asking such question is reinventing the wheel. People ask these questions since the beginning of their time, and so far they came up with the Golden rule as pretty much universal and fundamental. In other words, it is, as much other folk wisdom, pretty much time-proven meme.
You can only know (for sure) what you feel, what you like, what you want etc etc, or at least think you know, so what else to base your behavior on? On a doctrine about mythical "better" world, or imaginary "good"? Sure, if you would like to be treated by others acting on their own doctrines ;)