>>936115482
The harm isn't physical, it's because children are innocent and don't understand, *cannot* understand, sexual desire.
The harm comes when they reach sexual maturity and realise that they were used for sexual gratification by someone they trusted, doing something they thought was merely a game.
When they experience sexual desire for themselves, they feel like their innocent self was used, because they couldn't understand the implications of their actions, even if they enjoyed orgasms and intimacy.
It's tragic, really.