Steve Sanders, a proponent of SSM writing at the University of Chicago Law School Faculty Blog, registers some serious doubts about the wisdom of targeting DOMA's defender:

...as a lawyer who recently worked in the Supreme Court and appellate practice group of a major national law firm, I've found myself uncomfortable with the demonization of Clement and K&S and with the insistence by some gay-rights supporters that defending DOMA's constitutionality is not only legally wrong but morally unconscionable. Those who would label lawyers like Clement as (at best) amoral mercenaries do not understand how the world of public-law appellate litigation works.

... every constitutional lawyer knows there is a basic difference between whether something is sound policy, and whether it violates the Constitution. Clement's job in defending DOMA (he reportedly will continue the representation through another law firm) is about the latter question.

... It's worth remembering that until two months ago, the Obama administration's lawyers also defended DOMA. DOMA may be an easy question as a matter of fairness and equality, but its status as a matter of constitutional law -- particularly whether it should get heightened scrutiny -- is not a slam dunk, and its opponents would be well advised not to confuse the two issues.