Therefore I shall employ a simple heuristic; I shall assume that the option which does the most good when one person does it is also the option that does the most good when everyone does it.
This assumption seems trivially false to me, and despite being labeled as a mere ‘heuristic’, it is the crucial step in your argument. Can you explain why I should take it seriously?
I think this is the post you remember reading: http://www.sl4.org/archive/0207/4935.html