In a legal case with profound implications for LGBT rights and religion's place in public life, the opposing sides agree on this: It's not about the cake.

At its core, the case that goes before the U.S. Supreme Court for oral arguments on Dec. 5 is a showdown between a gay couple from Colorado and a Denver-area baker who in 2012 cited his Christian faith in refusing to make a cake for their wedding celebration.

Jack Phillips, owner of Masterpiece Cakeshop in Lakewood, was judged through multiple phases of litigation to have violated Colorado's anti-discrimination law. Through his lawyers, he n...