Opposing views during a march to the match are nothing new for Sounders fans.

But the animosity about 100 people encountered Sunday as they walked and chanted from Pioneer Square to a match against Sporting Kansas City was different.

A cluster of 11 men and one woman who pledged allegiance to the Proud Boys white-nationalist organization awaited the Sounders supporters outside the southwest end of CenturyLink Field. Some yelled expletives at the marchers, who wore T-shirts with Iron Front symbols or raised scarves that read “Anti-Fascist.”

The taunts were prompted in part from news of Emerald City Supporters — the independent supporters group of the Sounders, which has Sections 121, 122 and 123 as its designated seating area in the stadium — being warned about displaying an Iron Front flag at a July 21 match.

The Iron Front was an anti-Nazi paramilitary organization founded in Germany in the 1930s. Historical websites vary on the specific meaning behind the symbol — three arrows pointing southwest — but it is broadly accepted as anti-fascist.

Major League Soccer classified the Iron Front as political imagery and banned it from its stadiums under its revamped Fan Code of Conduct. But multiple supporters groups across MLS are challenging the league’s stance, particularly after the gunman for a mass shooting in El Paso, Texas, last week identified as a white nationalist.

“If anything, I believe, people are more empowered to do what they believe is right than maybe before,” said Tom Biro, co-president of ECS, of his fellow fans. “We are not a political organization, we will never be. We have stated our beliefs and our members have said now, more than ever (anti-fascist).”

Seattle police Lt. Brian Stampfl said his department increased the number of officers in Pioneer Square to 25 and designated four officers on bicycles to patrol near the Proud Boys at all times before the soccer match’s 7 p.m. kickoff. The only obvious incident was when the group tried to enter a bar known to be the gathering space for ECS before matches.

Sounders co-owner Drew Carey was in attendance and spoke with one of the Proud Boys members.

“So what? I don’t care,” said Carey of any concern, reiterating not flying the Iron Front flag is a league rule.

ECS is joined in support by other fan groups Gorilla FC, which identifies as the Antifa supporters group, and Sounders FC Alliance, which represents all season-ticket holders, in challenging the league about its definitions of political imagery. Also aligning with ECS is Portland’s 107 Independent Supporters Trust, which bills itself as “the engine that fuels the Timbers Army and Rose City Riveters,” the fan groups for the Portland Timbers MLS team and Portland Thorns women’s professional soccer team, respectively.

MLS commissioner Don Garber, in a recent ESPN interview, wouldn’t take a stance regarding “Make America Great Again” red hats worn by supporters of President Donald Trump. Garber did support the Pride flag, which has origins stemming from a riot at a New York City gay bar and is a foundation by the same name originated in 1985. Also, clubs such as Sporting KC will honor U.S. military-service members and their families by having players wear camouflage pre-match warmup tops. The league also sells camouflage merchandise online.

But Garber reiterated the league’s belief the Iron Front is a political organization and its imagery has been appropriated to entice violence.

“Our stadiums are not environments where our fans should be expressing political views because you then are automatically opening yourself up to allowing counterviews,” Garber told ESPN from the MLS All-Star Game in Orlando, Fla. “Then we’re getting into a situation which is unmanageable and really not why the vast, vast majority of fans go to games.”

ECS fans will be suspended for three home MLS matches if spotted flying the Iron Front flag. Shirts with the imagery are perceived to be permissible since dozens were seen by media and no one was reported removed from the stadium by security for that reason.

Still, Sounders front-office staff told media Friday it heard from many fans they don’t want any political imagery at soccer games.

“I know about the Iron Front but it’s not something I’m super interested, I just don’t care,” said Mike Berta of Kirkland, who has been a season-ticket holder since 2011. “It’s disappointing they (Proud Boys) are here because I do not agree with their values. This is a first for me.”