If you were lawyer would you donate your time to helping gay activists? Why would any true originalist work to overturn a law that was perfectly Constitutional?
It really wasn't. The Colorado law did not disallow making gays a protected class, like blacks, Jews and women. The law required refusal of government services to people who identified as gay. For example, a gay book club couldn't meet in a library. A gay bowling club could be denied the use of a community center. The real fear was that, down the road, city-owned hospital could deny treatment to gays. "This Colorado cannot do," Sandra wrote.
If Judge Roberts HAD to work with a "gay activist" wouldn't it be better, if he disagreed with the whole case, to do it pro bono rather than being paid. The payment would have been like Judas & the 30 pieces of silver. Rather blood-money-ish.