I can see zero difference in the information density between the existing non-responsive design of that page [0], and the beta version of the responsive design [1].
While your point that mobile first design inevitably causes a lack of information density at desktop resolutions has some merit, it does not apply in this case.
While your point that mobile first design inevitably causes a lack of information density at desktop resolutions has some merit, it does not apply in this case.
[0] http://cl.ly/UFuw
[1] http://cl.ly/UFzs