In the privacy of your own home or church, you can believe what you like and it is absolutely none of my business as long as you do not affect another person against their will.
Going out of your way to remove the comfort your chap derives from his faith for no good reason... It reminds me of David Thewliss's character destroying the nightwatchman in Naked (https://www.youtube.com/watch?v=N90sl94g7PE). Why would you, for no reason? Why would anyone? Why *should* you?
But, the moment you start pontificating about the right of women to control their fertility or be paid the same as men, or attempting to stop consenting adults to stop falling in love because they have the same shape genitals, or murdering innocent people in big buildings or down in tube stations or cutting bits off people, or saying it's OK to murder or otherwise deprive or infringe the rights of the bunch over yonder because your book says their god isn't real, or making my children attend compulsory religious services in school or restrict their ability to access education, or stop the teaching of robustly supported science because it contradicts your religious text of choice, or murdering film-makers or closing down plays because they dare criticise your religious text of choice or issuing death sentences against someone for drawing your prophet or or re-writing history or demanding special rights or tax exemptions or any other similar thing, you're fair game.