Aaron Starr has it exactly right above. Mike Seebeck nails the crucial point @52, which is that in the fantasy world where DPI gets on the ballot and actually passes, it will have successfully forced another look at the DOMA framework. In a game of chicken between DOMA and millions of married California taxpayers, I wouldn't want to be riding with DOMA. Federal rules would probably be rewritten to restore the status quo ante faster than you can say "AIG bonus", but that's the worst case scenario. Hurt me with the problem of the Obama/Pelosi Democrats scrambling to revise DOMA and trying to live up to their anti-DOMA rhetoric. I would love it if DPI forced a DOMA showdown, and I'll happily donate to Outright twice whatever extra tax liability DPI actually causes my wife and me. But two times zero is still zero, and it's mendacious for Rob to say we on ExCom "endorsed a massive federal tax hike".
Here in the Real World where DPI won't even make the ballot, Prop 8 is sure to be repealed sometime in the next decade, and the LPCA ExCom should support any effort (such as DPI) to do so. Endorsing DPI has the bonus of surfacing our issue of separating marriage and state, and that's a good thing. The only "resources" the LPCA is spending on DPI is agenda time and press-release space, both of which have very low marginal cost.
A first step to getting government out of marriage would be to stop calling the contracts that the government regulates "marriage". I don't buy Rob's argument that "marriage" is a word that Libertarians should try to take back from religion through political means. What Libertarians should care about is contract, not "marriage". The farther that we can separate the legal contract from all the cultural freight it's been carrying, the better. I too would enjoy the irony of the weight of government being turned against right-wing culture warriors who have used it to promote their moralistic conception of "marriage", but it's not the LP's job to change their conceptual landscape. The LP's job is just to stop them from legislating their morality. Disconnecting civil partnerships from the M-word would be a deft move in that effort.
Mike, YesOnEquality does now have an initiative in the pipeline for repealing Prop 8: http://www.sos.ca.gov/elections/elections_j.htm.
Rob, that IRS memo is in the context of domestic partnership being distinct from "marriage"/"matrimony"/"husband and wife" situations. In particular, the IRS memo cites the fact that California law at the time did not allow registered domestic partners to file joint income tax returns for California state tax purposes and to be taxed in the same manner as married couples for state income tax purposes. DPI would disallow the distinction that the IRS memo cited. The legal territory here is sufficiently uncharted that nobody can confidently predict the exact rulings that various bureaucrats would disgorge. However, one can easily predict how our legislators would react to the scenario you paint, and confidently making such predictions doesn't mean one is unlibertarian.
Debra, the LPCA ExCom that voted on this included half of Outright's four national officers, plus our Northern Vice Chair Rich Newell (the maker of the motion) has been another prominent Outright member. DPI would repeal Prop 8, and Rob's own press release alleges substantive harms (relative to the status quo) only to straight married Californians like me. Well, I for one am willing to take those risks. Nevertheless, we should reject the identity-politics notion that some of us are more qualified than the rest to speak up for liberty and against injustice. All rights are individual rights, and we are all individuals. (Insert obligatory Life Of Brian joke here.)
P.S. The Outright press release invites readers to conclude that Rob resigned to protest the DPI endorsement, but Rob has admitted that he had prepared his resignation letter before he even heard of the DPI resolution.