Many valid suggestions by many professionals and our friend, who seems to have tried everything, is still troubled.

Simple! Besides all else, hit them in their wallets. Everytime they strike a column, fine them, 2,3,5 dollars. Collect the money and use it for a company summertime bRbque or Christmasy thingy. Keeps you out of trouble with the union, should keep everyone from driving into the columns. And I am serious!