I still see the distinction that the person refusing to make the cake is refusing to make that kind of cake for everyone. Hence no discrimination. The other baker is perfectly willing to make wedding cakes, just not for gay weddings. So discrimination.
This is the way I see it. If, as a baker, I refuse to bake wedding cakes, period, I'm covered from having to bake one for a gay wedding. Who knows, maybe I don't bake cakes at all. Maybe it's because all I do are 1/2 sheet cakes and smaller, basically good for a civil wedding with a dozen attendees, and I have this printer thingy that does the decorating, so not exactly fancy.
I stick a policy up on the wall 'Too complex requests will be declined, no negative messages*, no violating federal discrimination laws'.
On the other hand, with the latter situation I might be 'forced' to make a simple cake for the gay 'wedding' that's a pure civil service with a dozen or so friends. In which case, if I was operating a bakery, especially given the news, I'd sell them their cake. Not worth the hassle, and their money spends just as good.
*The cancer test was negative! Congratuations! would probably be okay.