How can we set up a histronics-free discussion about potential diffs?

[AngusThermopyle]

The problem is, what is "the truth"?

To some, 'The Bell Curve' was "the truth", supported by 'facts'.
To others, it was a polemic, misrepresenting data.

If you can get a universally agreed upon definition of "intelligence", and a universally agreed upon way to measure it, we might have the start of a discussion.