The govt, of course, is not allowed to discriminate on grounds of race, sexual orientation, creed and a host of other similar issues1. But individuals in their daily lives constantly do so discriminate, in who they choose to interact with and how. They have liberty to do so. Then again, people have a "right" not to be discriminated against when out validating their lives by shopping.
How do you balance the two? In daily life, you expect reasonable people to disagree peacefully. If you can't get one baker to bake your cake, look for another. I haven't - of course - studied the fine details of the case but I'm pretty sure the said GF made no attempt to do this; indeed my suspicion is that they did the very opposite.
Twenty years ago this case would have been laughable, and would have been laughed out of court. Today, it makes it to the supreme court. Twenty years from now perhaps the custom will have shifted so far towards the GF that intransigent bakers will tremble with fear; I'd rather hope not. The SCOTUS decision, wisely, is narrow. This winds up my source but I think wrongly. Similarly, the digs at the overt hostility that the Colorado commission showed toward Phillips make sense. Really, the SCOTUS is trying to tell the idiot litigious children to play nicely together and stop bothering the adults; they don't want to make the same mistake the Pope made over Galileo.
1. So the USAnians bizarre Separate Car Act is unacceptable; the whole equal, but separate nonsense3 should remind us that all law requires interpretation.
2. In most people's framing, it is important that the baker's objections are religious. I don't see why that matters. In others, because of "deeply held beliefs". As far as I'm concerned, he simply didn't want to serve these customers for [reasons], exactly what those reasons are is unimportant.
3. This is part of, but not the entirely, of the necessary "of course this isn't the same as institutional racism in the USA during the Jim Crow era" argument. The precise means you use to distinguish it are somewhat up for grabs. Another is the "one-off" argument, but that smells of special pleading. Better is the "no compelled speech" idea; for example WE.
* Calling all German fans! says Terrible Real Estate Agent Photographs.
* When individuals become more autonomous, they become more social - TF.