As I see it, there are at least three issues here and maybe more. One is the issue you raise, that is, censorship. Does a company such as Amazon have the right to censor books because it does not agree with their message? A second issue, which is connected to the first, is the right of private companies to sell and not sell whatever they wish. Conservatives often say that private companies have this right, so why not in this case? A third issue is the sale of items that have potential harm to the welfare of the individual or of society, for example, selling a book that provides specific instructions on how to commit suicide or murder or take over the government. For some, this book, rather than helping them, actually harms people who are gay.