Yet out of all difficult questions I've ever discussed, this seems to be the hardest one to open a rational discussion about; the amount of sanctimoniousness and/or logical incoherence in the answers one typically gets is just staggering.

My experience is similar. Even people that are usually extremely rational go loopy.

One exception are several discussions I've read on Overcoming Bias, which at least asked the right questions, but unfortunately only scratched the surface in answering them.

I seem to recall one post there that specifically targeted the issue. But you did ask "what basis should" while Robin was just asserting a controversial is.