If not, then they should not be voting for Prop 8, which has been said to uphold "traditional" marriage.
I think that before we focus on who should be able to get married, we should focus on what marriage truly is. Is it just something you do in Vegas for fun? Is it something that has a duration of 5, 10 or 15 years? It is something that can be a "starter" or "trophy"? Is it something that can be cancelled out by a couple of signatures?
If I were a California voter, I would vote NO on Prop 8.