For what it's worth, I have just figured out an even easier way to contact members of professional organizations.  (I wish I had thought of this earlier, although my earlier method was far from onerous!).  I have modifed my standard letter to include the address of your petition; I really think that signing the petition is a wonderful way for us "outsiders" to register our concerns very easily.

By the way, some of the people who have already signed the petition are among the most eminent people in the field of literary studies, so you are getting not only quantity but also quality.