His comment took me a while to parse too. The way I ultimately interpreted his comment was "Since 1(d) = 2(r), it's only natural that 1(rotation) = 2(PI radians)". Which is ironic. I.e. the inequality between the coefficients is actually the tau-ists' primary argument against pi. Also, I don't know how it's relevant to its parent comment, which was about "1 rotation being defined as 360 degrees" being arbitrary.
The 360 isn't arbitrary, rather boils down to 60 arc-minutes and 60 arc-seconds, which of course is 3600 arc-seconds in circle. Where the 60 comes from:
