Do you really think that? You think there aren't white men who go after black kids specifically? Pedophiles will have their personal turn ons I'm afraid; they'll be after one thing more than something else. It's sickening to contemplate, but it would be stupid to not recognise it. The culture somebody grows up in may well influence and affect this choice.
Pedophilia occurs worldwide in every culture, nobody is suggesting it's a problem only specific to Asian men, just that in this specific case, it was white girls who were targeted.
Also, you seem very sure of yourself; do you know these people? How do you know race didn't come into it; have you had a personal conversation with them?
Did you know that most online grooming is carried out by white males (it's something like 90% of online pedophilia is carried out by white males)? What's your opinion on that? Do you think that's at all relevant? Do you think there's something about our culture that influences this?