It's not judgment it's common sense. If you're a fan of the team, you don't try to embarrass the team. Falcons' fans don't show up to games with 28-3 shirts...because if they did....They're NOT FANS! This isn't a hard concept. There's literally even a self-proclaimed Falcons fan saying this is a horrendous idea for someone claiming to be a fan of the team.
Get shirts printed up that say Aints for all I care, Boutte. But don't then try to give me some backwoods explanation about how no-really-I-am-a-fan "sad face". If you're in the dome wearing a bag, I'm lumping you in with the rival team's fans who also bought a ticket. Having a ticket doesn't make you a Saints fan. Plenty of Falcons fans will have tickets in a few weeks too. And they would be the only ones to appreciate idiots that show to the game with a bag on their heads. That makes you more a rival fan than a Saints fan in my book.