The Watchtower has always been good at saying things like, "If you knew there was a dangerous storm coming, wouldn't you feel a moral obligation to warn others about it??" This is the motivation for JWs to get out and preach "the end of the world" to the innocent public.
Once we know that the Watchtower is built on lies and fear and control...that they are not the "voice of God," then some of us are moved to tell "the truth" about "the" truth. It is natural to want some form of "revenge," but in that vein, I think this is more of a need to "heal" from the effects of being lied to; to find the strength to regain some sense of normalcy, and life in freedom.
By the way, the book: "30 Years A Watchtower Slave," by William J. Schnell, (published in 1956, available at http://www.bakerbooks.com), is a wonderful and enlightening book on how the society developed, and "perfected," mind control...beginning in Germany, and then practiced in America. I agree...the title does sound "negative," but back then, the Watchtower had many "classes" of JWs, and many were viewed as "slaves"; and the author is only stating in the title what he, himself, was to the Society.
I do hope that you will look into getting this book for yourselves. It is an easy read, and extremely informative!! It really gives the reader an understanding of how the society went from a simple publishing company (that let each congregation guide themselves) to this current All Controlling "Theocracy" Government.
I have read MANY books exposing the truth about the Watchtower Organization, but this one book really brings EVERYTHING into focus.
Thank you