May it never be said that I argued in support of the political courage of Hillary Clinton, but it's a bit ridiculous to fault her for opposing gay marriage at a time when over two-thirds of American adults and most Democratic politicians held the same position. How many viable Democratic presidential candidates, who have been national figures since at least the late nineties, can claim any better?
(On the other hand, it's slightly more difficult to shrug off Bill Clinton's signing of the Defense of Marriage Act, to say nothing of the implementation of Don't Ask Don't Tell, as anything other than both moral and political cowardice.)
DOMA, like much of the horrible 90s legislation, was passed by veto-proof majorities in Congress. If we didn't get that, we would've gotten a Federal Marriage Amendment which would've been much harder to get rid of. Same for DADT, which was actually an improvement over the previous policy of hunting down the gays by all means to kick them out.
Considering the toxic and vicious attitude toward gays in the 90s and early/mid 00s, holding off the worst excesses of the bigot agenda was the best that could be realistically hoped for. I mean, many states were still enforcing sodomy laws during this time.