I don't agree with everything he has to say, but I like him. I do tend to agree with him on the topic of religion. I think the reason that some people tend to dislike him so much isn't just his views, but rather the fact that he states them so unabashedly with no reservations whatsoever.
That's precisely it.
Religion is the topic he is most asked to debate about, ironically overwhelmingly by churches and theologians. He argues in the spirit of others before him; he takes no prisoners and makes the audience uncomfortable. That's his style; in the same way that his opponents appeal to different aspects of human nature such as fear of the unknown, or the self (or make appeals to a higher power). Richard Dawkins for example makes the same argument as Hitchens but is more calm, often reserved. Sam Harris is more 'chummy.' Christopher Hitchens has a similar (though I find less grating) style of debate and fluidity of argument as his brother Peter. Peter Hitchens is in my opinion ten times as odious.
When he is asked to discuss other matters, particularly politics, socialism and the Middle East he is the same man; it just so happens that people who may disagree with his stance on religion rally round when he talks about foreign policy. The substance of his debate however is never found to be lacking.