"Hurt is any form of pain or discomfort. Harm is something that costs you something you don't wish to pay. Millions of people around the world engage in sexualized pain play. Does it hurt? Yes. Does it perhaps leave an injury that must heal? Sometimes, yes. Is that a cost they mind paying? Not at all. Alternatively, consider sex and date rape. Sex is pleasurable, in the right context. In the moment, even, an intoxicated person may enjoy the sex they have while their judgment is compromised. But pleasurable experience could be considered harm, if their compromised judgment cost them something they weren't willing to pay.
"For an example closer to home, consider your clinical trial with Takemi this afternoon. You experienced significant discomfort, undertook a risk, even passed out. Did that experience harm you, however? Did it cost you anything you weren't willing to pay?"