I really think there should be an offence of having sex without due care or attention.If you hit someone with your car because you didn't believe there was anyone in the road is that ok? You didn't intend to harm anyone and believed the road was clear.I refuse to believe if he had taken any care or attention he wouldn't have realised this was a child, barely out of primary school.
There being a separate offence for that would be fairer.
I don't think it should be classified as rape if she consented, was not drunk, etc. I can believe that a 12 year old would voluntarly have sex with a 19 year old. (He could easily have looked 15, after all.) Statutory rape is a good thing when adult men rape girls, because it'd be horrible to ask a girl to prove she didn't want sex with an adult man! (It is horrible that the burden of proof is on the victim, anyway, but you know what I mean)
Being stupid about having sex is not the same as rape.
I have met underage boys who I would have mistaken for young adults from the level of their conversation, etc. (Actually, in my early to mid twenties, I was frequently hit on by boys, as I look a lot younger than I am, but when their pickup line is "In a year I am old enough to get a drivers' license and then I can drive you everywhere!" it is easy to tell the age ...)
A 19 year old would not be alerted to the girl being too young for him by talk of school and homework; he might even still be in school himself.
I don't know how the girl looked, and it could be a case of men willfully believing that any sexy-looking female must be over the age of consent, but without a picture, I really cannot judge that.