I imagine even the most nefariously brainwashed would have to concede that in the end it was their own choice to act.
Jonestown suiciders took their own lives. Suicide bombers pulled the pin.
Short of kidnapping, long-term indoctrination, and threats, accountability would be meaningless.
The initial brainwashing, in my opinion, often holds little to no choice for many individuals due to the typical circumstances behind it. I have watched it happen lots of times. The ignorance about what is being done to their minds combines with any pre-existing natural suceptability to it, and bam, there you go. The suceptability does not seem to be as big a problem as the ignorance, if they both exist in approximately the same degree. Information and knowledge before the fact can go a long way toward someone deciding it's time to get the hell up and walk away before things get out of hand.
Once that initial brainwashing is done and finished, and also the "honeymoon period" has passed, the question as to what kind of choice exists is complicated.
Part of what would go into a core cult member trying to make a choice to leave a cult (or disobey about something) depends on that person understanding that there IS a choice. That requires some level of critical thinking, as cult leaders endeavor to convince the victims that there is no valid choice other than cult involvement. And people's critical thinking skills, which are the tools they need to be able to help themselves in this event, are exactly what takes a big shit as a result of cult involvement.
It is like, for the person to be able to get out of the cult, they need to be able to hit a bullseye on a dartboard, but the cult environment has hidden all of the darts.
You would think that basic intelligence should make a critical difference in who will walk away from a cult at this stage and who won't, but for whatever whacked-out reason, in my experience it doesn't seem to. The dummies I saw leaving a large-ish cult I was observing might have been leaving for different reasons than the smart ones who did, but in the end, it was clear that at least in a statistical sense, "intelligence" was just not the defining factor. It could be the case that the smart people have more of a chance of recognizing that there is a real choice, but something else in the process cancels it out for them. The smart people, the ones you would think should know better, can stick around for a really, really long time.
The question of choice and accountability during the post-honeymoon stages of cult involvement seems complicated to me. Like... there are parents who have killed their kids because they refused to take them to the doctor due to cult beliefs. These were people whom I suspect had little-to-no real choice during the initial brainwashing, but when that initial superzealous state is over and done, what's the deal with what they could and could not have chosen to do in the circumstances?
Legally, I am pretty sure that the parents are found responsible if they kill their kids that way. That is a completely defensible and common-sense position on the matter, and a very easy one to agree with. But at the same time, it could also be possible for someone to place the blame squarely on the cult leader if he or she was the creator of the system, and the brainwasher, and the reenforcer of exactly this kind of behavior. That position could also be argued reasonably well.
Can both positions be right at the same time? or must it be just one, and which one would it be?