"They had ADDED material of interest to them as a Christian school. They have not SUBTRACTED anything"
I don't see anything in the the article that indicates the course met all the requirements for accreditation and merely added extra things. I've been through the accreditation process as the curriculum coordinator of a science department. The regional accredidaton association didn't have any problem with our religious curriculum (I also taught a Judeo-Christian religion class) - they were only interested in the academics, the overall environment in the school and the quality and educational background of the teachers.
That course teaches straight American History and examines the influence on it of Christianity as an ADDITIONAL level of interest.
Try doing the same thing to "African American Influence on American History."
Why is Christianity allowed to be discriminated against....and Christianity's influence is tremendous?