Ugh...stop. Took the bar last week. Plus...when applying the rational basis standard isn't the burden supposed to be on the challenger to show it's NOT rationally related to a legitimate purpose. The government doesn't have to prove anything under the rational basis test...I thought.
You're right, but I frequently (as I'm sure you've noticed) simplify a bit when writing about legal issues on jazzfanz.
What you identified actually magnifies my point: To wit, Prop 8 opponents were able to successfully demonstrate that Prop 8 is not rationally related to a legitimate state interest and the government couldn't prevent them from doing so. They don't have to do much to defend their law because all the burdens run the other way. The hurdle for the government was extremely low, they basically just had to not lose. They still lost.