Look, folks, it is all about the almighty dollar for large law firms. If they can receive $1 more by defending Lucifer himself, they will do it. But if Coca-Cola says, "Defend Lucifer and you won't be seeing any new business from us" then poor old Satan is out in the cold.
I am a little surprised, by the by, that $500,000 is sufficient to defend the Defense of Marriage Act. First off, there is probably a lot of discovery, etc. on the reasons behind the Act and whether there is a "rational basis" (or some higher standard) being met. There will be expert testomony and depositions, etc.
No way you can get this up to the U.S. Supreme Court at a large firm like King & Spaulding for $500,000.
Be that as it may, when your $40MM a year client (Coke) says, "Don't do that," you are likely to listen. The guy who left K&S to do the work anyway at a smaller firm says that the sure way to be on the wrong side of history is to abandon an unpopular client.
Uh, I don't think you understand the whole concept of "unpopular client" buddy. Read Caroline Products footnote #4 -- those discreet and insular minorities who are out of favor are the "unpopular clients" whom you should avoid screwing over. You aren't going to be on the right side of history, for example, by arguing for (and winning) Japanese-American internment camps were a good idea during WWII. I don't think anyone is out there saying, "Wow. Thank God that guy stood up for what is right and just!"
When I was at a large firm, a guy from a major corporation came in and argued in favor of hiring quotas. It was amazingly unconstitutional! "When I have a job posted, I say go get me five black candidates for this job....if they bring me only one, they are not doing their job. We need more black faces." Oh my lord. Some young associate (not me for once) questioned whether the blatant use of racial quotas was a legal business practice. The guy informed the firm's managing partner that "you guys have a long way to go" and demanded that the firm associates receive diversity training or he would pull his account.
So I got diversity training -- it was taught by some incredibly hot white woman, and it basically stated that "there is great value in diversity." Someone asked if she was advocating hiring quotas for black men and she stated, "No." OK -- lesson failure.