Silly, silly comment to make.
No way is sex ok for a 13 year old, regardless of her sexual partners age and whether they think they are in love. The only thing he has done is condone under-age sex. It's wrong, they have all the time in the world 16 and onwards to have an intimate relationship, he should be encouraging kids to seize the right to be children and hold onto it for as many years as they can.
The only grey area in my eyes as far as under-age sex is the one that our law already recognises. If someone is 15 when they are having sex but will turn 16 before any case will appear before the courts, what is the point? It will just be an expensive court case that would end up being thrown out of court.