Eric A. Posner has a theory that the reason California’s Proposition 8 wasn’t struck down by the U.S. Supreme Court this year is because of Justice Ruth Bader Ginsburg. Decades before the high court’s decision on that state’s same-sex marriage ban, the court ruled on Roe v. Wade — a decision Ginsburg argues came too quickly. In the 1970s, women’s rights were already expanding and would’ve continued on that path naturally, Ginsburg contends. Instead, the Roe decision sparked a …