Faith is, by definition, the rejection of reason.
Dictionary.com offers this as its first two definitions of the word "faith": "confidence or trust in a person or thing; belief that is not based on proof".
Unfortunately for those who put so much faith in faith, reason requires proof before accepting an assertion as fact. A belief not based on proof is not based on reason. Consciously choosing to have such a belief--even to declare it a virtue--is to reject reason.
There is little point in trying to reason with someone who has rejected reason. Or, as others have put it: You can't reason someone out of something they were never reasoned into in the first place. I tried it when I was younger without success. In fact, the closer I came to success, the more dangerous they became.
I think the axiom above should be re-stated to make the actual situation more clear: Reasoned discussions regarding matters taken on faith are oxymoronic. You can't reason a person out of a conviction that was adopted by rejecting reason.
A person with such a strong emotional need that he rejects reason is a person not in touch with reality or in control of himself. Such people are more comparable to wounded animals sulking in the back of a dark cave. Cornering them with logic can lead to vicious attacks.
The bad experiences I have had with believers have caused me to change my tactics. I finally realized that they have rejected reason because of emotional need (this is the very definition of delusion), and that the emotional need in question is usually egotism. I also finally realized that when they say fear of god is the only reason to be good, they are revealing their own utter lack of internal morality. People are at their most dangerous when their egos are threatened and people without internal morality are always dangerous.
As I pointed out in a previous post, faith is also a sign of a very dishonest thinker. One cannot have complete faith in a few completely unproven propositions while rejecting all the others for lack of proof without being completely dishonest. This level of dishonesty is also a sign of someone with no internal ethical standards. The attacks they direct at you will not usually be actual physical violence, rather, they will turn the same sort of completely biased eye on you that they turn on other religions. Everything about you will become "proof" of how evil you are. But, that tendency will be explored more in depth in another post.
These days, if I choose to engage a believer, I make sure that I am safe first, then I usually do no more than plant a couple of barbs of thought before breaking off the discussion or walking away entirely.