The transcript says
Derbyshire: Hang on a minute. Five years on average, yes they do Mr Clarke, yes they do.
Clarke: That includes date rape, 17-year-olds having intercourse with 15-year-olds.
If instead of reading it as a list, you read it as
Clarke: That includes date rape: 17-year-olds having intercourse with 15-year-olds.
then it makes perfect sense as he continues
Clarke: Serious rape, I don't think many judges give five years for a forcible rape, the tariff is longer than that. And a serious rape where, you know, violence and an unwilling woman, the tariff's much longer than that.
Otherwise it's saying that he doesn't think date rape as rape by someone you know is a forcible rape. That doesn't make sense. It makes far more sense if he was differentiating underage sex and forcible rape. The punctuation in the written transcript makes it read differently than I think it was meant.