The fact that some psychotic little twit off'd Lennon has nothing to do with Lennon's philosophy or the content of his songs. Chapman's motivation doesn't even qualify Lennon as a martyr, just a victim.

I can understand a religious organization banning (if that is the correct word) certain songs due to anti-religious content. Would you tolerate all four verses of "Bringing in the Sheaves" down at the local pub? Probably not. It's kinda like the right to associate.
Why try to make an issue of this? Unless you are anti-relgious?

As for reasonablilty, most any group has a lot of followers who are content to let some one else do their thinking for them. This is the mainstay of most political parties and it can be gauged by the number of slogans used as opposed to real ideas.

Theology and philosophy have long been bedfellows and religious thought has shaped the human mind for millenia. Our very language and thought patterns are steeped in it. You can't escape it.