Since I've blogged about this issue, I thought I'd let Barton testify for himself as to why Glenn Beck can be both a Christian and a Mormon at the same time.
Let me note I don't have a dog in this fight. On a personal matter an ecumenical universalistic theology appeals to me more than orthodox evangelical Christianity. Though the latter faith, as I often observe it, is quite narrow and exclusive in its truth claim.
And here is Beck, Barton and some other guy on the Christian Nation question.