New fan
It really all goes back to the Dome Patrol days. The Saints had one of the best defenses in NFL history, and one of the best teams in the NFL, but they never made it to the Super Bowl. The reason? The Atlanta freaking Falcons. In those days, the Saints won all but 2 or 3 games, and I think the Falcons barely had a winning record. It should be an easy win - in theory.
And, even though the Saints were one of the top 2 or 3 teams in the NFL in the regular season, the Falcons had the Saints number in the playoffs. The Saints would play the Falcons in the playoffs, and the Falcons didn't just beat the Saints, they made them look silly. They did that one year, then I think it was the very next year the Saints were in the same situation, playing the Falcons in the playoffs. So, you'd think after the defeat the year before, the Saints would come out ready for blood. Only they got spanked again, and never got close to the Superbowl again until Sean Payton and Drew Brees came along.
So, it's like the bully got beat up by the wimpy kid.
That and just nobody likes Atlanta, the city.
Something like that.