Here's my thoughts for any who cares to read them
Because for some unknown reason people (in general) want/need/crave a "belief" system. One that claims to answer the basic fundamental reasons of their existence. IE. where did I come from, why am I here & where am I going(especially after i die)
People find comfort in a message that seeks to answer those questions. People gravitate to those who voice a "favorable" message, one that fits into their own personal desires and expectations. Basically a person belongs to a religion that teaches and tells them what they like to hear
So now Joe is happy in his religion, happy with the message, happy with his life and were he "believes" he's going.
Jack comes along and says "What? You honestly believe THAT??? That's crazy man...THIS is the truth!"
Jack proceeds to tell Jack all about HIS religion which may or may not have over lapping beliefs. At which point Joe has a choice, decide that Jack's religion promises a better future and has better answers to life's questions...OR he tell Jack that, no he's wrong and he's been mislead and it really HIS (Joe) religion that right.
They could at that point decide to go their own ways and call each other dump for believing in the wrong beliefs. Sometimes this happens, but only for a short period of time. Because the problem is now there's doubt, however small...the Jack's of the world become a threat to Joe's believe system by virtue of their own existence. It becomes if they're right then I'm wrong...and I KNOW I'm not wrong so they are wrong and they're spreading all their lies and leading others astray and contrary to the beliefs that I KNOW are right and true.
It then becomes Joe's duty to protect the integrity and truth of what he believes and has been told/taught is true.
It's the basic "If you're not with us, you're against us" philosophy.
To actually answer the OP's question....it's because a person's been raised or taught a certain belief system from day one. It's part of life and natural just as breathing is. That person is not going to look kindly on someone showing up and telling them that they're wrong. That they've believed the wrong thing ALL of their life. Oh yea...ALL of you friend and family and all your ancestors were wrong too lol
It kind of destroys the foundation of their very existence to even entertain the possibility that they indeed might be wrong.
The other possibility is that a person is simply unhappy or unsatisfied with the teachings or beliefs of the belief system they find themselves in. Yet they still have the need and craving to have a purpose and direction...so they search out and try and find one the "sounds" like something they can accept as "truth" and as the way it is.
I was raised in a pretty religious family. Went every Sunday and the thought of NOT going actually never entered my mind.
But years have passed since then and I'm not the person I once was. Because of my childhood and what I was taught I have a mind's eye of what I'd like things to be, what I HOPE things are and will be. But to actually come out and say that I know for sure that I'm 100% right or that someone else's beliefs are 100% wrong??? I find the whole process and ordeal absurd.
We (well most) have HOPE...that's all it boils down to. We hope that we have an idea of what to expect when we die. An idea for why we're here and why things happen in the world the way they do.
But when someone, anyone tries to tell me they KNOW for sure...I walk the other way. I've removed myself from the game. I neither praise, nor condemn any belief system. Except!!! for any that choose to actually harm (emotionally or physically) another that has a different belief/system. That in my opinion is the very hight of hypocrisy and is as close to pure evil I think one can get. (well one of the ways
)
I have my ideas, my hopes based on my own study and philosophical thoughts. I'll know one day if I'm close to the truth or not.
One day I'll take my last breath here and my eyes will close...
I HOPE that they open again.
If that happens then I'll go from there
And I expect it'll be one hell of an adventure if that does occur lol
Regards to All
Roland