I agree with @Christopher except his last statement about Helen. Helen definitely had a "sexy" and "playful" attitude.
Turn it around. Imagine a male psychiatrist hypnotizing a female patient into thinking that she wanted to have sex with him. That would obviously be a sexual assault. But our culture has a gendered double standard and falsely assumes that a woman can't sexually assault a man. But it's not about gender, it's about power. If you have power over someone, if they're unable to give or withhold consent and you take advantage of that to do something sexual, that is a violation.
They had already confirmed that it was very effective at implanting a suggestion without the patient's knowledge, when she made Kirk think he was hungry. So she already knew she could implant desires in him, and she implanted the suggestion that he desired her. That was taking advantage.
One other thing that was cut from the episode was an explanation that Kirk had only danced with Helen at the Christmas party because he'd thought she was a visitor rather than a crewmember. That's why he was so embarrassed and uncomfortable when he learned she was part of his crew -- because, contrary to Kirk's later reputation, he was a responsible, ethical commander who would never try to romance a woman under his command (which was why he fought his attraction to Rand so fiercely, as seen in "The Naked Time" and elsewhere). So the scenario that Helen implanted, even before Adams took over and amplified it, was one that portrayed Kirk violating his own professional ethics. Hardly a frivolous indulgence.
That's one way of looking at it, but the episode never identified it as a related device; rather, the production just reused the prop to save money, the same way that the Elba II control room in the same episode reused the semicircular console that had previously been seen as Landru's brainwashing console, the Romulans' cloaking device console, and others. We certainly were not meant to believe all the uses of that console were actually the same technology; it was just a reused television prop. And the same goes for the treatment chair.
Of course, in-universe, it's entirely possible that the chair design and the emitter design are standard components used in numerous pieces of therapeutic technology. No need to reinvent the wheel every time; the external parts could be off-the-shelf tech and the differences are inside.
