Unfortunately, there are many (esp. new Christians) who do get their doctrine from song lyrics.
Yep. That's why it's our responsibility as older Christians to bring our younger brothers and sisters along. It's also why we have to define, very carefully, what we want our "Christian" music to do. Do we want it to be a sermon in three and a half minutes, or do we just want an alternative to the crap coming out of the secular labels?
Neither position is wrong. There are bands and labels who *do* write 3 1/2 minute sermons, and those guys are great. There are also bands who simply write songs from a Christian worldview, and those guys are fine too.
Then there's me. I'm just a hack guitar player. :)