am torn on this.
On the one hand I wouldn't like it if a daughter of mine (I don't have daughters but ykwim) was going out with someone that much older. Simmilarly I wouldn't be happy if my ds was going out with someone that much younger.
But I'm not sure I agree that the man is necessarily creepy or that fifteen year olds aren't and shouldn't be attractive because they're children. The reality is that many fifteen year olds look and act way above their years and that as a society we have become guilty of encouraging this to a degree, with support offered to young teenage parents for instance etc.
As a society we are beginning to see fifteen year olds less as children and more as upcoming adults, allowing them to dress in adult clothes, wear adult make-up etc. There are many fifteen year olds round here who could get into an over eighteen nightclub without needing to persuade anyone of their age.
I'm also not entirely sure that telling her that him having sex with her is rape etc is helpful. If she were going out with a sixteen year old I doubt that people would be so quick to suggest this, and would probably even be talking to her about safe sex, and while advising would probably be open to the possibility that it might happen anyway.
She has to IMO learn for herself. And the more people that object, the more she will rebelle. Just make sure she is safe, and the relationship will run its course eventually if that's what's meant to be.
I went out with a 21 year old when I was fifteen. He was very immature and I was very mature. He wasn't creepy or sleezy, ultimately the relationship fizzled because I grew up and he didn't, and he genuinely loved me. I remember his mum seeming very against us being together, although she always treated me well, welcomed me into her home etc, but she seemed distant sometimes, and it's only with hindsight that I realize it must have been because she was concerned about the age gap.