Are you saying that a 13 year old girl with no sexual experience who agrees to have sex with a sexually experienced 21 year old hasn't likely been manipulated and coerced?
Does anyone have statistics comparing the occurance of teenage pregnancy (or underage sex) between those with significant age differences and those without? Otherwise I would expect most underage sex to occur with both parties underage.
The same goes with a young boy and an adult woman. Was it OK for that female teacher to have an affair with her 13 year old student? I don't think so.
Did the boy mind? I read an interesting article written by a a guy who had sex with his parents child minder when he was 12 to 13 (she was twentyish, IIRC). He thought it was great. She was prosecuted.