The same logic could be applied to religious books produced by the main religions. At times of religious tension there could equally be protest at the distasteful and unsavory content (the advent of the internet has given every sad case campaigner a wonderful platform with which to get organized). The answer wouldn't be a ban.
No it couldn't. Why would a book about / promoting one of the 'main religions' be sure to sell no copies? I'm not advocating the store declining to sell something provocative. I'm suggesting that their choice to not stock this book in Liverpool, can be viewed purely as a sane business decision.