In the narrowest sense, Dr. Carson's remarks may have been inappropriate for the occasion.
The problem is that the occasion itself is so absurd that normal behavior and comments seem abnormal by comparison.
A group of conservatives and liberals professing different faiths or no faith at all hanging around pretending that their religious views are somehow compatible? Now that's an absurd occasion.
By speaking the unvarnished truth, Dr. Carson committed the sort of faux pas one makes by being fully clothed at a nudist camp. He is the only one there doing the right thing, and so he seems out of place.