What do you think the alternative is? You want the government to mandate that every book store carries all books? Book stores have a right to curate their selection as they see fit in exactly the same way that authors have a right to write what they see fit.
It’s censorship, I didn’t make any judgments about when censorship should be allowed/encouraged. It’s just the literal definition of censorship and you’re being defensive because you think it’s a bad thing.