From rectitude + -in- + -arian.
rectitudinarian (plural rectitudinarians)
- A person who has a high standard of rectitude
2009 April 12, Wyatt Mason, “Laureate of the Louche”, in New York Times[1]:William Logan, a critical rectitudinarian, called Seidel a “name dropper” whose books trade in “jet-set tastes and upmarket sinning.”