When I look back at my evangelical Christian upbringing, I clearly recognize that vigorously championing my beliefs was actually a way of concealing my own doubts from others and myself. This is the mechanism of self-deception:
“When a person, who disbelieves p, intentionally tries to make himself believe or continue believing p by engaging in such activities, and, as a result unintentionally misleads himself into believing or continuing to believe p via biased thinking, he deceives himself in a way appropriate for self-deception. No deceitful intention is required for this.”
I’m not saying that self-deception is always the motivation, but I surely wasn’t alone.