"Ugly new circuits, ugly cars, no engine sound. F1 is dead," it declared.
The protest, handwritten in blue and red ink on a white sheet, was still there long after practice for the Italian Grand Prix had finished and the fans gone home.
The irony of someone buying an expensive ticket, at one of Formula One's oldest and most atmospheric racetracks, in order to declare a lack of interest was not lost on those in the garages opposite.
"I don't think that one banner sums up the overall opinion about Formula One," said Ferrari principal Marco Mattiacci, while others made light of it.
"Whose garage was it opposite? McLaren?," joked Red Bull's Christian Horner.
"I think I recognise people from Formula E (the new electric series starting next week) putting that banner there," laughed Lotus deputy principal Federico Gastaldi. "This is a fantastic race, it's history. Come on."
"It seems a very strange place to talk about ugly circuits," agreed Marussia's John Booth. "One of the most iconic circuits we go to."
If there is one place on the Formula One calendar where the true, original spirit of the sport lives on, then Monza would be high on most people's lists along with Spa, Silverstone and Monaco.
The old banking, disused since the 1960s when the track featured in the climax of the 1966 John Frankenheimer directed movie 'Grand Prix' with the late James Garner and a cast of drivers of that era, remains a place of pilgrimage for many.
The Ferrari 'tifosi' still swarm through the turnstiles, trudging through the wooded park outside Milan and flooding the finish straight after the race in a red tidal wave of national passion.
And the racing this season has, by general consent, been thrilling with Mercedes team mates Lewis Hamilton and Nico Rosberg in a duel for the title.
Yet the banner reflected the feelings of those followers who feel the sport, with its new and quieter V6 turbo hybrid engines and energy recovery systems and races in ever more exotic locations, no longer excites.
Ferrari are not winning as before either, with the glory days of Michael Schumacher a distant memory, and the sport struggles to make the front pages of even Italy's soccer-obsessed Gazzetta dello Sport daily.
Former Renault team boss Flavio Briatore articulated some sympathy with unhappy fans when he visited the circuit as a guest of F1 supremo Bernie Ecclestone, himself a vocal critic of the new engines.
"It is a new F1. Maybe it is better, but a lot of people don't understand. It is as simple as that," he said.
(Editing by Ed Osmond)
