Kamasutra is not a religious text. Religious texts talk of how to realize Brahman, what sacrifices to perform and how, hymns to the Devas, or Bhasyas on the preceding...to what Veda does the Kamasutra belong? To which school of Vedanta does it belong? Who has commented on it - Madhura, Ramanuja, Sankara?
The Kamasutra was never considered a religious text in India until 19th century Western orientalists came upon it and used it as another example of why Christianity was superior to 'pagan' Hinduism. The modern Western neo-orientalists in Western academia have continued this myth. They dare not do this to the Christians as they would lose their jobs and tenure. Some good Hindu arguments to see are in Chapter 8 'De-Spiritualizing Tantra' in Invading The Sacred: An Analysis of Hinduism Studies in America. The entire book is available as a free download at http://rajivmalhotra.com/books/invading-sacred/
Some of the conclusions at the end of Chapter 8 are:
"According to many members of the Hindu diaspora, the implications of the White-Doniger thesis for the study of India and Indic traditions has been disastrous. Malhotra summarizes the impact:
White gives ammunition to those who attack Hinduism as being a collection of barbaric practices.
He tries to undermine Hinduism's spiritual claims and renders its philosophical texts as fake or hypocritical.
He feeds Hinduphobia in the minds of mainstream Americans who see everyday Hindu symbols as weird and/or as representing immoral practices."
further on he states: "What they [Hindu critics of this Western academics] do criticize is the attempt to reduce Hinduism to pornography and to wish away the profound spiritual component in Hinduism."