Portland, Oregon (CNN) In this stereotyped mecca of liberal idealism lies a deep-seated subculture that just recently shocked the country: the white supremacist movement in Portland.

Not long ago, that phrase might have seemed oxymoronic. But a recent triple stabbing has cast a spotlight on the city's tensions between the alt-right and the alt-left.

"Portland has a long history of a battle between the right and the left," said Randy Blazak, a professor of criminology at the University of Oregon.

It's a long-simmering conflict that heated up after President Donald Trump's election. And experts say Portland -- like other liberal hotbeds -- could see more conflict in the months to come.

'You call it terrorism, I call it patriotism'

The most recent feud played out both inside and outside a hearing for slaying suspect Jeremy Joseph Christian

Christian is accused of fatally stabbing two men who tried to protect two African-American girls, including one wearing a hijab, on a Portland light-rail train.

"Go home, we need American here!" Christian shouted at the girls, according to a probable cause affidavit. "I don't care if you are ISIS."

On Tuesday, Christian had barely entered the courtroom when he started shouting in his blue jail uniform.

"Free speech or die, Portland!" Christian bellowed. "... Death to the enemies of America. ... You call it terrorism, I call it patriotism. You hear me? Die."

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Just outside the courtroom, vitriol flew from the other direction.

One man identified himself as a friend of Christian's and was instantly met with profanity from some supporters of the victims.

"F*cking Nazi, you're a fascist!" one person shouted at the man.

"I bled for my race," he replied, as he tightened the red shoelaces on his boots.

Red shoelaces have historically been used by racist skinheads "to identify themselves as white power skinheads," the Anti-Defamation League said.

It's not clear what the man meant when he said he bled for his race. Sheriff's deputies escorted him out before any more trouble erupted.

It's far from the first time Portland has been linked to Nazi extremism.

Flashback to 1988 murder

At the Portland metro station where bloody victims emerged last week, mourners wrote messages in chalk to honor those killed.

One message stirred memories of another gruesome murder: "Remember Mulugeta Seraw."

A message in front of Portland's Hollywood metro station honors murder victim Mulugeta Seraw.

"The murder of Mulugeta Seraw really put Portland on the map for all the wrong reasons," said Blazak, who is also chairman of the Oregon Coalition Against Hate Crimes.

Seraw, an Ethiopian immigrant, was bludgeoned to death with a baseball bat by a group of Portland skinheads in 1988.

"This city had a wake-up call," Blazak said. "It was kind of a sleepy, progressive city where we recycled everything. And then all of a sudden we had these roving gangs with Nazi skinheads attacking -- and in this case killing -- an immigrant."

'Skinhead City'

Skinheads had been known to recruit from the heavily white states of Oregon, Washington and Idaho -- part of a "Northwest Imperative," The Oregonian reported.

And in the years following Seraw's death, Portland gained the unsavory nickname of "Skinhead City."

"We became famous in the 1990s as 'Skinhead City' because of the rival gangs of right-wing racist skinheads and anti-racist skinheads who are doing physical battle in the streets," Blazak said.

Last week's deadly train incident "is kind of the latest manifestation of that," he said.

Protests on the rise since the election

In recent years, Portland has enjoyed a reputation as a friendly, peace-loving, quirky city -- an image further fueled by its portrayal in the IFC comedy " Portlandia ."

But conflicts have escalated in recent months, Portland Police Chief Mike Marshman said.

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"With the election of President Trump, I think our protest activity -- the number of events we have -- has increased," he said.

"That's problematic for me only because that takes more money to have those events go safely. I have to pull officers and detectives from their normal day-to-day activity, so certain crimes just now aren't getting investigated, or the investigations that are being worked