Fair enough, the news that a 15 year old girl is sexually active is not exactly going to stop the presses.
Fair enough, the difference between sexual activity at 15 years 364 days and 16 years is (in the UK) one of legal status for consent.
Fair enough, a 15 year is perfectly capable of initiating sexual activity.
What is not fair enough is to give a married man in his 30s ANY slack or sympathy for allowing a relationship to develop with a 15 year old. He was the adult. He was aware of the law. To call the relationship inappropriate is an understatement. It is simply wrong.
Even if a 15 year could legally consent to sex, it does not make this sort of relationship appropriate or healthy.