Considering who initiated the case that has (temporarily, for now) stopped “Don’t Ask, Don’t Tell”, I suspect at least part of the motivation of the Obama administration in fighting to keep what they themselves have claimed to want to repeal is a particular irrational fear. The fear I refer to is that being able to attribute what, ostensibly*, would be a gay rights “win” to a group of Republicans in court (as opposed to Democrats in congress) would somehow shift voters who care about gay issues towards the GOP. Sure, this completely ignores the fact that the Log Cabin Republicans are treated like a one-legged mule by their own party, which continues to recruit candidates who sound one step away from advocating that all non straight evangelical christian folk be burned at the stake, but I did say it was irrational.
(* – Wanting to join the empire isn’t exactly what I think of when it comes to rights. To each his own though I guess. Whatever, gov’t should be non-discriminatory until it is non-existent.)