So, you can believe whatever you want, as long as you don't act on your beliefs?
> ... to a political movement specifically pursuing institutional discrimination of a large class of Americans.
Prop 8 was proposed by the voters of California, it would not have had direct ramifications on the rest of the US.
> ... blatantly unconstitutional...
The last big ruling by the SCOTUS on gay marriage came down to a 5-4 vote. The supreme court justices are not amateurs at enforcing the US Constitution. That it was 5-4 is a good sign that the issue is hard to argue one way or the other from the constitution.