The goal and practical effect of Prop 8 was to keep gay people from equal treatment under the law. In particular, to strip them of the ability to marry.
We have no idea what Eich's ideas are, because he has refused to say. But I can and will judge him by his actions. And no, I don't believe that's a straw man. I don't believe it's possible to have a rational and consistent view that includes both the 14th amendment (explicitly naming equality before the law as a civil right) and using the power of the law to keep gay couples from marrying like any other couple.
If you really want to attack his ideas, attack their best interpretation, not their worst.