U.S. Sen. Dick Durbin is convening an important hearing in Washington today to examine the threat of domestic extremism and hate crime in the wake of the horrific attack on Sikh worshippers in Wisconsin last month.

If the hearing in the Senate Judiciary Committee’s Subcommittee on the Constitution, Civil Rights and Human Rights does nothing else but put additional pressure on the Department of Homeland Security (DHS) to take far-right extremism seriously, it will be worthwhile.

In 2009, the DHS caved to criticism from the political right and essentially gutted its unit that monitored non-Islamic domestic terrorism. The action came after heated but misguided criticism from right-wing commentators about a leaked DHS report – an entirely accurate and prescient report, in fact – that warned of a rising threat of terrorism from various sectors of the radical right. Most members of the unit left the agency after enduring what they considered unjustified criticism from within the DHS. The agency now claims the unit is fully functional, but the lead author of the 2009 report, former DHS analyst Daryl Johnson, says that isn’t the case.

In testimony submitted to Durbin’s panel today, Heidi Beirich, director of the SPLC’s Intelligence Project, urged federal vigilance in the face of what strong evidence suggests is a rising threat.

Earlier this year, the SPLC reported that the ranks of far-right extremist groups had swelled to record levels in the past three years, a period coinciding with the Obama administration. The SPLC is tracking 1,018 hate groups – a 69 percent increase since 2000. But the most explosive, recent growth has come among antigovernment “Patriot” groups, which have increased by 755% in the past three years – from 149 groups in 2008 to 1,274 in 2011.

Members of both hate groups and Patriot groups have been arrested or otherwise implicated in terror plots in recent months.

Wade Michael Page, the shooter in the Aug. 5 attack in Wisconsin, was a musician who performed with a variety of white supremacist bands and also a member of the Northern Hammerskins, a faction of one of the most violent, racist skinhead gangs in the country. On Aug. 5, he walked into the Sikh Temple of Wisconsin, in the Milwaukee suburb of Oak Creek, and killed six Sikhs and wounded four other people, including a police officer, before shooting himself in the head.

That attack was the latest in a series of violent acts and criminal plots by extremists in recent months and years.

In November, for example, the FBI arrested four members of a Georgia militia who were accused of various crimes in a plot to kill federal officials and attack cities with the deadly ricin toxin. In May, members of the American Front, a militia-style white supremacist group, were arrested in Florida for planning acts of violence and preparing for “an inevitable race war.”