Most professionals believe the contrary. Hassan's clearly expresses in his book that the cult indoctrinated individual has not changed. He continues to be a loving, concerned individual who wants to do the best for himself and his family. What has been changed is the framework under which the decisions are made. Therefore, most of the responsibility seats on those who purposely manipulated the enviromment. This is not a black and white thing. The more indoctrinated you are, the less empowered you are to make "rational", decisions (I use quotes because from the view of the cult personalities, their decisions are more than rational)
In my view, to say that the individual is always ultimately responsible, is like saying no one would ever be unfit to stand trial in a court of law. People should be tried regardless. Most individuals who are unfit to stand trial are ultimately held responsible and may go to jail anyway. The difference is that in most of this cases, the jail is a means to prevent another crime, not a punishment or a means to re adapt them.
Indoctrination is a very powerful force. Look at advertising for an example. I have a sister in law, who after 10 years of not setting a foot in a KH, went to read jwfacts and her hands began to sweat. A cousin of my wife, also inactive for a long time, is taking on an alternative diet in order to increase her red blood cell count in preparation for a surgery that would normally require blood. She assures the world in facebook she needs to accomplish this "because of her belief"