Back when I was a good and loyal JW, I used to take strong exception to accusations that we, as JWs, were "brainwashed."
The expression "brainwashing" first appeared into usage during the Korean War (1950-1953), when it was used to describe the treatment meted out by the communists on allied prisoners of war. (Another name suggested for the process is "Menticide" - i.e. the complete destruction of the mind).
After researching the methods used by the communists to "brainwash" allied POWs, the only resemblance that I could see (and still can see) between this and the JWs is possibly the indoctrination process. Even that, though, while being somewhat similar in form, is nowhere close in degree. Also, indoctrination is only one of many parts to "brainwashing" a person. Prominently featured in the process are such cruelties as starvation, freezing in an unheated prison cell during the depths of a Korean winter, and the withholding of medical treatment - all the while keeping a person awake for days at a time, with three shifts of interrogators mentally tormenting him without letup.
I had to conclude from that that those who accused the JWs of being brainwashed had no idea what the process actually involved, and that the term was being used more as some sort of a religious swear word than an accurate description of anything.
(There is plenty of excellent material available about the brainwashing processes used by the communist countries. One such work I found particularly interesting was General Dean's Story. Dean was a senior American general, captured during the opening phases of the Korean War, and who endured three years of brainwashing while being held as a prisoner of war.)