He was, obviously, raised in a homophobic society and is so repressed he refuses to be comfortable with who is, in fact, is.
To ban this book (and other he publishes) has nothing to do with freedom of expression, because even this liberty has boundaries that one should not cross. For instance, to promote discrimination, to give false hopes (there is no record of one successful "conversion"), to elude the readers, and to raise hate for those who are different.
The author fails to understand that nature promotes diversity, not uniformity and although he has all the right to live or don't live is sexuality he should not sell these lies.
The idea of this book is offensive and I know that if the author defended that women are inferior to men or that white people is superior to black people this book was already removed from Amazon.