The girl has SORT OF defended him, saying that he was only 17 at the time, and did not have any idea of her age. The Sun has published the exchange of messages though, which do make him seem not just creepy, but also a pretty unpleasant lad.
Basically along the lines of:
JM: You've got lovely...
According to today's gutter press, the REAL reason was NOT those old tweets at all, but rather, private facebook messages that he sent to a 14 year old fan, asking she send him photos of her breasts.
That's not a great career move.