The gay sex book is being sold by Amazon and so it is obviously in demand and it is common that people buy more than one book at a time and so it will have an associated book link.

I don't see the big deal. Maybe it would be different if the associated purchase for the gay sex book was something like "The art of unprotected sex"

It seems prejudiced to make an issue out of the fact that a gay person buys a book on spirituality....did you think all gay people bought were dirty sex books or what?