Nadolo and Exeter number eight Richard Baxter were sent to the sin-bin as the officials tried to regain control and it was the Fijian wing who rounded off the evening when he returned to score a late consolation try.
Haughton's score, which came four minutes into stoppage time after he rounded two forwards on the wing, broke the hearts of a Viadana side that have yet to win a game in this year's competition.