Do you know what the cake was supposed to look like? Because if it was just a normal wedding cake that looks similar regardless of who's getting married, your example doesn't apply. If it had a couple gay guys or gay gals kissing, then maybe the example applies. If it was just a normal cake, then they were denied solely for being gay, not for asking for a "gay cake." And if it was just a normal cake, the example would be that a German asked for a portrait of his dad or maybe a landscape, unrelated to Nazis, to be painted.