( 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 , saidÂ 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 are n'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 is n'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 do n'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 . Sherrod resigned . 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 .
`` Extremists on both sides '' are stirred up , the Southern Poverty Law Center says . The New Black Panther Party offers a reward for George Zimmerman 's capture . One group says `` white nationalists are trying to inject their poison '' into the case . Anonymous Internet comments fan the flames , experts say .