System safety is my primary reason for advocating grounding the coax shield and mast.
In the cited gatech article, it appears that the author has not completely shielded the antenna. Rather they simply produced a more directional antenna, which is an effective means to receive less interfering signal from the sides and rear while receiving as much or more desired signal from the front.
Operation of coax shielding is explained briefly in the following. Grounding adds little if any improvement in the inherent shield properties of properly connected coax.
http://en.wikipedia.org/wiki/Electromagnetic_shielding
http://en.wikipedia.org/wiki/Faraday_cage
To stop the antenna from receiving all interfering signals would require shielding it completely which would also prevent the antenna from receiving desired signals.
If the assertion is that, 'grounding the coax shield somehow reduces the antennas reception of interfering signals', I disagree.