I'm not splitting hairs about my main point, which is that Leys doesn't actually respond to Hitchens's main criticism.
But let me respond about "obscenity":
You call Mother Theresa "respectiable". Hitchens's whole book advances the argument that she is nothing but, and is in fact contemptible. His argument is not germane to your point, so I won't delve into it.
Hitchens, in a video (you can find it on youtube, can't remember the title), argues that laughing at religious authority is important, and that religion should be mock, because mockery is one of the first steps towards overthrowing an oppressor. So the argument that we can't talk about a "respectable nun" in profane and coarse terms, and instead must treat her with ignorant reverance, is poisonous and cuts to the foundation of Hitchens's argument.
"It (the title) is actually a perfect triple entendre: the book is about the politics of missionaries and the position of those who feel they can enlighten by divine warrant and presume to instruct the rest of us not just in morality but in day-to-day conduct. It was a title I couldn’t not use."
[edit: http://www.youtube.com/watch?v=8t4VhQX5Ckk
"Mockery of religion is one of the most essential things because to demystify supposedly 'holy text dictated by god' and show that they are man made and what you have to show [is] there internal inconsistencies and absurdities. One of the beginnings of human emancipation is the ability to laugh at authority..."]