Well, there you go.
God didn't say to establish "non-denominational churches". God determined what Christianity was, but it was people who WROTE down those teachings and made it clear in human society EXACTLY what being a Christian means. Many heretics and false prophets in early Christianity were exposed and their heresies rebuked. If the term isn't defined for society, then the word is meaningless and anyone can claim to be a "Christian"
I agree with posts #91 and #112. She can get away with calling herself a "devout Christian" because she switched from Southern Baptist to a "non-denomination church" where you can believe ANYTHING as long as you "follow" Jesus. That's the problem. Muslims will tell you they "follow" Jesus too and believe he's a prophet sent by God, that doesn't make them "Christians". Carrie Underwood thinks she "follows Jesus" and that makes her a "devout Christian". If she was in an established Christian church that had a long history of following Christian doctrines and a clear set of values that followed what Christianity teaches, she couldn't claim to be a "devout" member. If she tried promoting "gay marriage" in a Christian church that follows TRADITIONAL biblical teaching about gays (even churches with vastly different theological outlooks like Roman Catholic or Lutheran Church - Missouri Synod), she would get in trouble with her pastor.
Jimmy Carter ended up leaving the SBC (and becoming an "independent" Baptist) for the exact same reason -- his liberal beliefs conflicted with what his church was teaching.
The only way she could get away with that in an established "Christian" church is to join one that has de-evolved down to "Christian" in name only and losing members in droves, like United Church of Christ. And even a really liberal church like UCC STILL has to maintain some basic Christian theology to use the word "Christian". You could probably even deny the trinity exists and be a "good Christian" in her "non-denominational" Church, since anything goes.
>> BTW, I prefer Coke. <<
Ah, but if you perfered generic "cola", you could get any product and claim you're drinking "cola", even if bears no resemblence to REAL cola brands like Pepsi, Coke, RC, etc.