First of all, adults should not be having sex with minors...period. But the LGBTQ Nation article is incomplete. This excerpt from the original LA Times article adds a little more depth to the discussion:
Sexual intercourse "is unique in its potential to result in pregnancy and parenthood," Justice Marvin R. Baxter wrote for the court. "The support of children conceived as a result of unlawful sexual intercourse provide more than just a plausible basis" for distinguishing the sex crimes.
What this seems to say is that it's okay for straight people to have sex with 16- and 17-year-olds if a pregnancy results, and the adult is willing to support the child (or is it more accurate to say "children" since one of the parents is still a minor?). In other words, it condones "unlawful sexual intercourse" if it results in teen pregnancy. This alone seems backwards.