The Massachusetts chapter of the Knights of Columbus vaguely blames somebody for forcing it to stay away:

We deeply regret that some have decided to use this occasion to further the narrow objectives of certain special interests, which has subjected this occasion to undeserved division and controversy. In addition, certain groups have chosen to misrepresent our reason for marching, insisting that we were participating in the parade to support another group or for political reasons. Such allegations are complete fabrications and have no basis in reality whatsoever. Because the parade has become politicized and divisive, and because of the misrepresentation of our motive for participating, we will not be marching in this year’s parade. Instead we invite Catholics to join us in prayer to celebrate St. Patrick during the hours of the parade.