– Wearing his Vikings-themed leisure suit, Justin Rustad expected jeers as he walked through the Eagles crowd before the NFC Championship Game last week.

As a Vikings season ticket-holder who frequently makes the road trips, Rustad, of Two Harbors, Minn., knows the drill: Opposing team fans heckle him when he visits their stadiums, and he dishes it out while tailgating at home. He does it with a smile, he said, and often ends it by offering a beer and good luck.

But after Rustad got shoved and cursed in Philadelphia, he pronounced the environment hateful: “We had people tell us, ‘This is how we are.’ ” he said. “Well, why? You can change your behavior.” Maybe, those who study fan behavior say. But it won’t happen easily or quickly.

With some of the NFL’s most obnoxious fans meeting up in Minneapolis for Sunday’s Super Bowl clash between Philadelphia and New England, sports psychologists and sociologists say that fan group behavior — good and bad — can be difficult to change. Deep loyalties to sports teams form early in life and are often passed down through generations, establishing a culture of conduct surrounding teams that is encouraged and celebrated.

“Different fan groups have different sets of norms of how they behave … what they do and don’t do, their traditions, their cheers,” said Nicole LaVoi, a social psychologist of sports at the University of Minnesota. “The only way norms really get changed is if a majority of people in that culture buy the norm. If all of a sudden the NFL said, ‘We want our fans to be the best fans, the most respectful fans’ … it’s basically lip service unless the fans themselves say ‘This is how we do it.’ ”

Some taunting and poor behavior happens at all major sports events, sports psychologists say. But how does a fan culture degenerate into something that gets a bad reputation?

Research shows people “will do things in the context of sport that they would never do outside of the context of sport,” LaVoi said. “People feel like they get permission, that it’s OK to act in these ways during a game.”

The anonymity that comes with being one of many at a stadium helps fans feel uninhibited, said Rick Grieve, a professor of psychology at Western Kentucky University.

It’s the intensity and frequency of the behavior that earns reputations, analysts say.

A subset of what some psychologists call “dysfunctional fans” — those who enjoy confronting others at games — can have a big impact, even though they are in the minority.

“If you’ve got a crowd of 60,000 people and 500 of them want a bad reputation, that’s about all it takes,” said Dan Wann, a psychology professor at Murray State University in Kentucky.

Vikings fans and media observers recounted many incidents of poor treatment in Philadelphia. In addition to fans being pelted with cans of beer and vulgarities, one Eagles fan stuck phallic symbols in people’s faces, others made sexual gestures.

After a young boy screamed in the face of a middle-aged woman in purple, a man who appeared to be his father apparently approved, smiling and saying, “Gotta raise ’em right.”

Later, inside McGlinchey’s Bar in downtown Philadelphia, city residents gave varying explanations for the Eagles fan reputation.

“New York and D.C., they get more of the spotlight,” said Al Davis, who works at the bar. “Nobody gives us respect. … You fight for it … the whole ‘Rocky’ attitude.”

Patron Jimmy Stephens said he’s never been an Eagles fan — or a fan of the fans.

“You see … drunken meatheads here booing Millie. What’s wrong with you all?” Stephens asked about Eagles fans shouting curses about 99-year-old Vikings fan Millie Wall. “The city wonders why they’re always the underdog. Why wouldn’t they be if they treat people like [expletive]?”

Even if most fans want their culture to change, it would take time and effort, sports psychologists said.

For the majority of fans who disparage poor behavior, fandom may make it difficult to intervene, Grieve explained.

Studies have shown that the more people are connected to a local team, the better psychosocial health they have, Grieve explained. They are less lonely and more trusting of people around them.

Fans of any sport typically think favorably of their fellow fans, Grieve said.

“If I see that person acting poorly, I’m going to give them a pass,” Grieve said.

But that’s not an excuse, he added: “The people who aren’t doing it, but aren’t stopping it, are also culpable.”

Wann said bystanders are sometimes afraid to confront aggressors, particularly if there’s the potential for violence and police won’t be able to tell who is intervening.

Karen Lundgren, of Edina, said one Eagles fan made a big difference at the NFC Championship Game when others taunted her and her son.

The woman put her hand in the face of one taunter and said “turn around,” Lundgren recalled. And he did. “Just one lady, that’s all it took to change an experience,” Lundgren said.

Psychologists said changing a culture is possible, but it would require promoting a new image at all levels, from the city to the team owners, coaches and players. Then fans have to be willing to embrace it, they said.

Both Philadelphia Mayor Jim Kenney and the city’s Convention & Visitors Bureau put out statements last week, with the mayor calling the actions of the “knucklehead” fans “disgusting and regrettable.”

“We’re certain they represent a small portion of the team’s loyal and passionate fan base, but the simple fact is that no visiting fan should have to put up with such treatment,” Kenney said.

The visitors bureau said leaders were disappointed by the inappropriate behavior of some fans, but praised those who sent money to Vikings Coach Mike Zimmer’s foundation, many of whom sent apologies with their donations.

Time will tell whether Minnesotans will see bad behavior on the streets of Twin Cities this Super Bowl weekend.

A few Eagles fans in town Wednesday to soak in the pregame atmosphere said they didn’t expect trouble. The game against the Vikings was history and they held no grudge against Minnesotans, they said.

Every fan base has people who cross the line, Philadelphia included, they acknowledged.

“We get a bad rap, and a lot of it’s deserved, a lot of it’s not,” said Jared Meshey, of Lancaster, Pa., as he took a break at the Mall of America to eat a Shake Shack burger.

Meshey and a few fellow fans had been watching their favorite sports personalities and former athletes on radio row when they broke into an Eagles chant a few times. A Minnesotan then asked them if they wouldn’t mind keeping it down, they said.

“When you get told that, you want to become louder,” said Andrew Bender, also of Lancaster. If the Vikings had won, he pointed out, “this whole place would be purple and cheering loud. Don’t take it away from us.”