I love the question and all the responses. I have a hard time determining what my "A-HA!" moment was.
Background - I was born in to a father was professes to be of the annointed and was presiding overseer. That was until we moved to another state and he was treated like a heretic.
I was appointed a Ministerial Servant at 19 and had every privilege one could be given as such. It was at this point I had my first real doubt.
1. I was working at a Circuit Assembly in the Accounts Department. We had a talk in which a major teaching flip-flopped. The original teaching was that brothers could not accept alternative non-military service when drafted. The new teaching was that you could. Many of the brothers in our circuit lived and worked in a major university city. They were young men during the Vietnam War and new many brothers who went to prison because they refused military service AND non-military compulsory service. One brother was told by the draft board he could work at the post office in lieu of military service. I saw how this impacted these brothers and it effected me deeply.
2. Out of college I got a job with a local police department in a non-sworn (no firearm) position. I was assigned to assist our detectives. One detective was in charge of child crimes. A brother in the local congregation was accused of molesting a child in that congregation. I saw first hand how these elders refused to cooperate and dodged subpoena service so they would not have to testify. That was a huge eye opener.
3. Years later I took a job that caused me to miss most meetings and field service was almost existent. I went with my parents to the District Convention. On they way home after the last day my father and I were sharing favorite memories of being a Witness in our home state. Then my dad dropped a bomb on me - he said there was a circuit overseer there that was targeting brothers who professed to be of the annointed for disfellowshipping. My dad was certain that if we had not moved he would have been next.
4. A few year after that I moved to another state. Shortly there after I was completely inactive. I worked a graveyard shift job and was reading a book a work week. I read a book about Mars and the evidence that supports that Mars may have had life millions of years ago. That lead me to read other things science related. The big science related fact I soon learned was that the global flood described in Genesis could not have happened.
5. I went to the police academy. It was there that we discussed using deadly force. The instructor shared Romans 13:1-7 and said that it was referred to as the "Police Officer Scripture" by leaders of many christian faiths. I also learned that "Thou Shall Not Kill" is actually "Thou Shall Not Murder" and how other Mosaic Law scriptures proved this. I had denied myself a career in law enforcement for over 15 years because I was taught Witnesses could not carrying weapons to defend themselves or others.
6. The final nail in the coffin was simply attending my final Memorial. My father would call me every years an encourage me to go. He told me it was important to make this one. The first thing I experienced was embarrassment in attending. The new song book had been released and I had no clue. Second thing I noticed was that it was the exact same outline used every year for every Memorial I had ever attended. The next day at work I visited this website for the first time. That was all it took. I was done for good.