I think we've decided as a society that sexual orientation is a protected group. You cannot discriminate based on sexual orientation. But I think you can still discriminate based on views of what is racist and what is not? If a white guy walks into black-owned barber shop and throws around racial slurs at the barbers, can the owners of that barber shop refuse him service and kick him out? I certainly hope so... but am I being hypocritical?
Honestly I'm out of my depth here. I have opinions but I don't think my opinions are necessarily as informed as I want them to be.
What kind of example is this? Does it matter what the respective races are? How is this equivalent to the wedding-cake example?
As for "sexual orientation is a protected group"; religion is also protected.
The truth is, there is already plenty interference is private business, but it (seems) to not be evenly applied. If I request a library stock (or borrow) a book that I'd like to read, I don't consider political aesthetics to be a valid reason to refuse.
> I'm sure there are plenty of Christian book stores / libraries out there who are unwilling to stock The God Delusion
Do you mean a normal bookstore owned by Christians, or a specialist bookstore that only stocks christian literature? If the store could refuse any non-christian material (e.g. a cookbook) as well as Dawkins books, I'm not sure if that's censorship - a greengrocer can also refuse to stock The God Delusion on similarly reasonable grounds.