Some people need the reassurance that they have signed on to something bigger than themselves that has all the answers and cannot be second-guessed. It absolves them of intellectual struggle. You'll notice posts that do not actually elaborate on anything or answer any question directly but, rather, just state their church's position as though that's explaining anything to the reader.
These people are often insecure when dealing with issues and ideas that are not black and white. Alas, much in life is NOT black and white, not even when it comes to religion.
Then too, some people like to feel pride of ownership, that "my team is better than your team." Racial superiority, ethnic snobbery, old beats young or young is better than old, etc. are all versions of this very human failing. They're doing the same thing with religion, except trying to justify it by a misuse of the Bible or, in some cases, something that is said by them to be better than the Bible--and only used by their variety of religion, of course.