why do people sometimes take religion to the extreme?

I dont write this to offend anyone but honestly why do some people take religion to the extreme? I am a catholic and am a proud one but you dont see me going around telling everyone the word of the Lord. I dont go around to peoples houses telling them if they believe or not. And why do people always say "it says in the bible" when the bible could have been changed long time ago. How can can you tell you were not alive then? People decide who they are and they decide what they should do not a book that was written a long time ago. And like i said i do believe in the Lord but i honestly dont believe the bible is 100%. For example can you read the bible and honestly believe everything in it is true? Yes there were miracles, and stories that did occur but i dont think that everything it says is true. I believe that there are more than just one Gods and we should accept them fairly. I cannot say that God is the only creator and i can only believe or worship Him. I cannot go to a Hindu and tell him he is all wrong, I cant tell the Native Americans that they worship something that does not exist? No because they will bring the same question to me, how do you know that God exists? Like i said i believe God put us here for a reason but i dont believe people should make such a big deal about religion.