I think this is the underlying reason so many players get more upset with losing control over their character, even temporarily, than they do with a character's death. Many players really enjoy the feeling of having control over their actions in a game that they don't really have in real life.
I agree that a feeling of meaningful control is one of the central appeals of roleplaying. Losing control of a character, however, can mean different things. It's probably safe to say that nobody likes it if their character is taken over by the GM so that they have to sit and watch the game for the next few hours. But at most tables I've played at, it's not uncommon for a character to be temporarily possessed or mind-controlled or cursed so that their personality and goals change. Some players dislike this just as much. Others dive in with gusto: a berserk barbarian savagely attacking the party wizard, a possessed knight suddenly acting in a decidedly unchivalrous fashion, etc.
My own character was once possessed by some sort of malevolent being. I found it surprisingly freeing as a player. I didn't have to think about the consequences of my choices for the party, or for the character that I'd invested so much love into. I was just a devious evil scoundrel until the party eventually figured it out a few sessions later and managed an exorcism. It was gloriously fun.