you have to consider it from a psychological perspective
we learn things we consider to be true from what we consider to be 'authority figures', which dictates how much truth we personally attribute to a piece of information. this is a lot more relevant in many cases (as with religions in the western world where information is freely available), than the validity of the information itself. imagine, his father, mother, uncles, aunties, brothers sisters, community leaders are all giving him a message (even though it's incorrect) that tells him one thing, it's very very hard to undo that shit.
one of the points i made much earlier, only because it stands in a book and is sold and read a million times, does not make it true. That but often is the tenor in casual discussions, such and such many christians cant be wrong ... or over thousands of years this is now the case and only because you come and say different ...
If you are in a point of a discussion, where the believer does not find arguments , but repeats parols, you need to give him time and not put him into the corner. Afterall we are just animals and would react devensivly, just let the information sinck in and hope that at a later point for an epiphany. This may now sound condescending for the christian folks at first, then again you can do it the other way round equaly ;)
I agree on the authority figure statement of importance and relevance to the frozen state of believes, although i disagree that that would be the only or even best solution to convince someone of a different way, not a bad way though neither. 'Stetig Tropfen höhlte den Stein', repetition is important too. As maybe experiences good or bad, where none believers would be helpfull with how and what they say and help through actions too. Live examplatory lives as none believers, then you may even become partly an authority figure you mentioned or just be a normal human being with all the inherint flaws, problems and struggles and still stand your ground in bad times as a none-believer =)
In the end, if religions don't adept, get rid of the BS put in books by some backwards minded sheperds(well 2000 years back they had been super hip ^^, but now a few of the values have a patina). If they don't adept, they will be exchanged or just cease to exist, simple as that, happened hundreds of times before, will happen again, no doubt there whatsoever.
Also when you look especially at cristianity, all the holy days in the year ... wich are different from country to country ^^ ... adaption for a broader publicum is what they do normaly, so there is hope for 'better/newer/uptodate' religions.
Trying not to be a dick, is for anyone who wants to make a point a good rule in my book.