It depends on the context.This is a poor example, and misses the mark. The case in point refers to intervening in an individual's selfhood, and compromising the integrity of their consciousness.
Better - but still inadequate examples - might include lobotomizing psychiatric patients, unsanctioned anaesthesia, spiking someone with LSD without their consent, or administering large doses of lithium sulfate to Alzheimer's sufferers in order to pacify them. How do you feel about those?
Spiking someone's drink at a bar is obviously evil.
Tranquilizing someone who has a gun to a child's head? Absolutely not evil (leaving aside the fact that this sort of thing really only works on tv because they'd have time to pull the trigger before the tranq kicked in).
Although, if you think that prison doesn't compromise one's selfhood I daresay you haven't known anyone who has spent significant time there. I have some friends who spent years behind bars, and based on my conversations with them, I think they would strongly disagree with your opinion.