The problem with likening pedophilia to gay marriage is that it's comparing apples and oranges - and also rehashing an argument that was made against interracial marriages. Really, you didn't see dogs marrying cats and chaos in the streets after interracial marriage was allowed. Why would you then see it when allowing same-sex marriage?
Instituting civil unions for those gay people over there and marriage for the properly hetero people over here has also been proven wrong - or did you forget the spectacular failure of separate-but-equal in 20th-century southern America? There really is no religious issue, since churches have full control over their parishes and can choose without anyone's interference to allow or disallow gay marriage in their own little worlds. Nobody can interfere with that. It is sacrosanct. What is at stake here is not the afterlife, but civil rights under the law, which is supposed to be separate from any one church. Considering that some (Christian!) churches are allowing gay marriage and some are not, this is a bit of a problem. Christianity itself is difficult to extricate from our government - consider all the religious symbols on our money, for chrissake. But in my personal opinion, the governments are cherry-picking the choice of church... which is wrong.
As far as I'm concerned, let men marry men and women marry women. If you're really all that concerned about it, drop a grant for a research study or twelve. Hungry grad students everywhere will be very grateful.
However, what makes Prop 8 hairy is that the prior law that was on the books was passed by the state Supreme Court. Prop 8 itself was passed due to popular vote. As far as I am concerned, popular vote should trump a court ruling any day of the week - which means that I fully support the decision in California to amend their constitution. Both sides fought very hard, but there had to be a loser, and neither side was going to be happy with losing. The population of California has spoken, though. State legislators should listen.
As for the Mormon church, though, I believe that they need to realise (as Hairy said earlier) that they made a national movement very, very angry. If they didn't know they were going to do so, they are idiots. Thus, they chose to campaign, and now they are getting decisive feedback from the community against which they chose to agitate. Suck it up and deal.