I'll also refer you to nihilistic_kid's post on the subject.
While I realize it's nice for a MSNBC broadcaster to come out for gay marriage, he, like protesters on Saturday, will be largely ignored by the mainstream and condemned by the social conservatives.
And since someone on my friends list felt free to condemn anyone who won't be attending a protest on Saturday...
I have to work. Getting bent out of shape about something that happened in California doesn't pay the bills, doesn't put food on the table, and sure as hell doesn't get me any closer to being involved with someone who I'd actually be tempted to use the right Prop 8 took away.
While I agree that I think California was wrong in voting in Prop 8, I think that religious institutions should not have been pouring money into the campaign to pass it, this is also an issue CA is going to have to work out with itself. Particularly considering how many states currently have Amendments banning same-sex marriage amd the federal DOMA law. If you want to protest something, try those. They affect us much more than an injustice in CA.
Also, as has been pointed out previously, CA still has domestic partnerships, which while not enough, are still a damn sight better than what most of us mid-westerners qualify for.