I'd say cointelpro and related ops has done a damned good job of programming generally. Like fish in water, we don't notice it because it is so pervasive.
Prof Mattias Desmet who writes and studies what he calls "mass formations" has said that they can be naturally deprogrammed by being in a society of non-brainwashed people, but he is only theorizing (i.e., no evidence).
I've seen hardcore Lefties who were thoroughly brainwashed in liberal colleges retain their hardcore Left beliefs even when they worked around solid free-marketeers on Wall St. Now that I look back on it, I find it shocking.