(CNN) -- The national conversation over Trayvon Martin's killing is loud and intense. In some places, it's also vile and violent.
The case -- in which a Hispanic neighborhood watch volunteer killed the unarmed black teen in Sanford, Florida, on February 26 -- has sparked a national controversy. It has also stoked extremist views, particularly on the Internet, experts say.
George Zimmerman said he shot Martin in self-defense after the teen attacked him. Martin's family has disputed that.
Investigators have not charged Zimmerman.
The Southern Poverty Law Center, the civil rights group that fights bigotry, said the case has stirred up "extremists on both sides of the racial divide."
A visitor to the website of one white supremacist group, for example, left a comment calling Martin "a punk negroe who messed with the wrong guy."
Meanwhile, the New Black Panther Party has offered a $10,000 reward for anyone who "captures" Zimmerman, an offer that Martin's family has condemned.
The Institute for Research & Education on Human Rights, which fights bigotry, said that "white nationalists are trying to inject their poison" into the case, too, portraying the teen as a "scary black man who deserved what he got."
"They have defamed Martin, concocted false allegations and amplified racial stereotypes of young black men -- in effect, putting the victim on trial in the court of public opinion," the group said.
Mark Potok, an expert on extremists for the Southern Poverty Law Center, says white supremacist attitudes often emerge during such hot-button controversies.
"You see this every time there really is something like this," an attempt to portray victims as perpetrators and this slain 17-year-old as a "gangster thug," he said.
The incident has created a "mob mentality," according to a commentary from William Bennett, a CNN contributor who served as secretary of education under President Reagan.
"The facts are confounding and inconclusive. But the tendency in the first days by some, including Al Sharpton, Jesse Jackson and an angry chorus of followers, was to rush to judgment with little regard for fairness, due process, or respect for the terrible death of a young man," Bennett said.
He noted that film director Spike Lee tweeted what he thought was Zimmerman's home address.
It turned out to be the wrong address, though, and it "resulted in an older couple fleeing from their home and fearing for their lives after threats and crowds outside their residence."
Lee apologized to the couple and said he would pay the couple's cost of leaving their home.
Lester Spence, an assistant professor of political science at Johns Hopkins University, said he's not surprised to hear about hate speech sprouting up. He said the Internet intensifies it.
"As soon as something like this happens, bloggers focus on it. People that follow them share that content," he said.
He said the hate shows up in comments under stories and essays on the Web -- comments that almost always aren't signed by the writers.
"People will say what they want to say under the cover of anonymity," he said.
"Go to almost any website that deals with this issue," Spence said. If there are no filters, the hate pours through, he said.
Kelly McBride, senior faculty member for ethics at Poynter Institute, a nonprofit school for journalists in St. Petersburg, Florida, said she isn't surprised that extremist talk has emerged in this case.
"There have always been people who believe racist things and those people have existed on a continuum," she said.
Hate speech involving immigration and sexual orientation also ripples across the Web.
People who don't pay "super close attention to these issues may not notice the hate speech on a regular basis," she said.
"The Internet affords people anonymity and insulation," she said.
Potok said the Martin case reminds him of what happened with Shirley Sherrod, the black Agriculture Department employee who was engulfed in controversy two years ago.
Late blogger Andrew Breitbart posted an edited and incomplete video of a speech by Sherrod, making her appear to say she discriminated against a white farmer looking for assistance.
A full version of the speech, however, showed that Sherrod had assisted the farmer. The department later offered Sherrod her job back when it was clear she had been misrepresented.
Potok noted that she was briefly portrayed as anti-white and was briefly demonized. He compared the slams at Sherrod to the doubt cast on Martin's character.