You said I made up his defense, yet you just re-iterated it. He said she lied (i.e., he was tricked) about being of age. She left little doubt that's what she did. Had she not, he would have been arrested, as legally, she is not competent to consent.
If she was 16, would you say she is still not someone to be protected? 15? What if she was 14 and is on tape telling everyone she is 18 and was looking to run up "her numbers"? What's your cutoff here? The "Model Penal Code" allows this defense with victims as young as 10 years old.