He seems to think that customers have a right to force their morality upon business owners and that not wanting to kill another human being is a "completely arbitrary and unnecessary basis" upon which to decide how to excercize your liberty.
Let's say there's a restaurant that refuses to serve veal for ethical reasons. What do you do if you want veal? Don't eat there! You have no right to force anyone to sell a product that they do not want to sell, regardless of the reason they refuse to sell it. You have no right to force them to comply to your morals.
Them not selling BC is no more forcing their morality on you than a store closing on Sunday forces their religion on you.
If I run any sort of business, I have the right to choose what products to sell. I could open a candy shop and refuse to sell Jujubees because I think they're part of an evil plot to turn toddlers into smores. You still have no right to tell me what products to carry. If I'm looking for jujubees, I loose you as a customer.
I could sell clothes and arbitrarily not carry blue socks.
I could close on Sunday even if "cultural homogeneity" means every other business in town is closed on Sunday too.