You know what is infinitely more disturbing than a 28 year old man carrying on an affair with a 15 year old girl? A 28 year old man having a platonic friendship with a 15 year old girl.
I myself am 28 years old and work in an environment with adolescent girls. NOT THAT I WOULD EVER DO IT, but I could see how a grown man would consider pursuing a sexual relationship with some of them. However it would take a true deviant for an adult male to befriend one.