There is the possibility that we are looking at this the wrong way. Is it possible that non-christians and non-whites simply want nothing to do with the republican party rather than the other way around?
That seems reasonable. Should we therefore expect that non-Christian, non-whites would be over-represented in the only other viable party? I haven't checked, yet, but I doubt that it is the case.
I think its clear that a disproportionate number of blacks, hispanics, jews, and atheists would identify as democrats
Sure, but the article was referencing elected officials, in Congress.