I agree Bernard, I should have explained myself a little clearer, sorry.
What I was getting at, is to me - and I'm sure most people - is that a there is not that much difference in appearance between a 15 and 18 year old girl. Girl's finish puberty in those three years, so if you are driven to seek out young women then why not go for the legal 18 and overs rather than those who aren't?
Why risk everything - his career and possibly wife and family - for the sake of a 'number' - 15, 16 or 17 rather than 18, 19 or above?
I guess the younger girls are more naieve at that age but I doubt any of them up for internet sex are hardly going to be virgins, if that is what he was after?
Either way he's a dirty old man - I can only speak for myself but at my age if I saw a girl walking down the street at that sort of age, with her mum - my eyes automatically look at the mother.
Either way as a parent I wouldn't want a perv like this anywhere near my daughter let alone teaching her!