Confused - why to Christians (and other religions) work over time trying to overcome someone else's beliefs, ideas, etc?

Funny, because a day or two ago I wrote some threads that indicated that the Sumerian writings predated the Bible, etc. Its like the entire thread was hijacked from zealots trying to prove otherwise, with many posts being some what abusive. Why? Hey, I'm all about keeping an open mind and pursuing knowledge, I just understand why some get so riled up to "prove" their religion/idealogies, etc.???

Really am at a loss, I don't understand the anger, bitterness, and win at all costs dogma?