Indoctrination causes this. The most vehement people have been so inundated with their church, their parents, their friends, their Sunday school lessons, their weekly sermons that they no longer think for themselves. They accept as "truth" whatever their family and friends believe.
And since most of the religionists spend their entire days, weeks, nights, and lives judging others, it becomes a way of life. They are CONSTANTLY comparing their beliefs to today's society and judging the perceived and slanted presentations of the media to their inner "moral" compass which is so skewed that they have no idea what truth is anymore.
They also live in constant fear that they might "get it wrong", so they are seeking reassurance from their "holy" books which are so lagging behind in societal norm that they can't possibly figure it out.
The most belligerent and stubborn types of these people constantly copy/paste bible passages and tract literature that do not even pertain to the current discussion! They vehemently INSIST that society is wrong and they are right. Or they simply refuse to READ and understand what is being written by non-religious people.
These people are in a narrow world and it is truly black and white only. They simply have no capacity for seeing reality.