There are two major factual inaccuracies in this thread here.
First, Hermesmann was a case heard by the Kansas Supreme Court, not the U.S. Supreme Court. There's no federal question here and it is binding in Kansas, not in the rest of the United States.
Second, Hermesmann in no way holds that 13-year-olds can technically consent to sex. It held that under Kansas' child support laws, parents have a legal duty to financially support their offspring, and this duty is not abrogated even when the offspring's conception was a criminal act (i.e. statutory rape).
I think the outcome is fucked up, but legally, this is an issue for the Kansas state legislature to resolve, not the state judiciary.