Whether you believe in Prop 8 or not, judges, supposedly, derive their power to overturn legislation based on laws' purported conflicts with The Constitution -- it is the Constitution from which their power derives entirely.
How on earth can they claim that constitutions themselves are unconstitutional?
This is a simple admission that they do not base their opinions on the Constitution at all, but simply upon their own sense of That Which Is Good. Shorn of any theory which even plausibly hints at such a residuum of judicial power, their decisions are now lawless and themselves unconstitutional, without even a pretext of principled, limited theory of judicial intervention legitimizing their actions.
If the judiciary steps in and claiming that legally executed amendments are a unconstitutional... then that is a serious, serious breach of separation of powers.
Essentially, the courts will deny one of the few checks on their power.
That's more worrying than anything related to gay rights.