Why is religion such a touchy subject? What's the problem with having a rational discussion of religious matters?
Maybe it's that religion is introduced to children before they're able to think. By the time they reach the age of reason they've lost sight of the fact that religion doesn't stand upon the same precautionary foundations as parental warnings that knives cut you or fire burns you. Neither is it in the category of practical advice such as encouraging you to obtaining a good education and a rewarding job if you want to support a family or achieve social status.
As a result, accustomed all his life to treat historical documents, newspapers, broadcast or social media and other purveyors of second-hand information with proper scepticism, the well-educated religious adherent may never even notice his inconsistency in failing to apply similar stringent appraisal to his chosen holy book or priestly dictum. (I certainly didn't until relatively recently.) If it should be brought to his attention, his instinctive reaction is often, at least initially, hostile. After all, what part of his world view is more fundamental than his faith?
Unquestioned certainties are rare and precious in a world full of shifting political, social and scientific sands. They are something firm to cling to, a source of support in time of trouble. Of all the stories he was told as a child, these religious stories alone have retained their power to cheer the adult. Their very familiarity is comforting.
Yet an outsider might see in the believer's antipathy to challenge or close scrutiny a subconscious insecurity. A good debater is always aware that to lose his temper is to lose the argument; anger can be an outward manifestation of an inner uncertainty. Can he marshal sufficient grounds of rebuttal to unwelcome questions?
He must know that what is accepted on authority rather than upon rational grounds would not be expected to stand up to examination in any sphere other than religion. Why in this one respect should critique not be allowed? It seems to me that a simple willingness to engage in discussion rather than resorting to angry denunciation and brute force would solve so many of the world's problems. What is there to be afraid of?
As J S Mill pointed out more than a century ago, if you're right you can't be proved wrong.