I don't like flags in the sanctuary, and I really don't like the "Christian" flag.
For one, I think it looks suspiciously like this...
I can
kinda see the point of a "Christian" flag as decoration in the more iconoclastic, bare bones sort of churches, the ones that look like a theater or warehouse more than a church, but the churches I go to usually already have a lot of Christian imagery, crosses and crucifixes and other decorations, and in the liturgical colors. There that flag just looks out of place besides being tacky.
But I have a real problem with swearing allegiance to it.
Even then I don't like it. I don't think it's appropriate for a Church to celebrate secular State holidays in the Divine Service, like what I saw at the church I was at this Memorial Day, where the sermon was
all about America and the military, with a bit about how Jesus died for you, like the soldiers, tacked on the end. It was even worse since that was (supposed to be) Trinity Sunday.