Fifteen years ago today, 168 people died in the Oklahoma City bombing – an attack that, at the time, was the greatest act of terrorism on U.S. soil. Among the dead were 19 children under the age of six. More than 680 others were injured. The perpetrators of that unspeakable act were members of a right-wing militia and patriot movement that gained steam in the 1990s.

Today, that movement is resurgent, fueled by hard economic times, anti-immigrant sentiment, hatred of government, a distaste for taxes, and disapproval of a black president named Barack Hussein Obama. Once again, extremist groups are backing up their rhetoric with acts of violence, and it seems that America has learned little since 1995.

The co-conspirators in the Oklahoma City bombing — army buddies Timothy McVeigh and Terry Nichols — blew up a truck filled with explosives outside of the Alfred P. Murrah Building. McVeigh, who was awarded a Bronze star and other medals in the Gulf War, harbored anti-government sentiments. Specifically, he resented the government’s handling of the 1992 siege at Ruby Ridge, Idaho, and the 1993 shootout and fire at the Branch Davidian compound in Waco, Texas, which left cult leader David Koresh and 76 followers, including over 20 children dead. McVeigh timed the bombing of the Murrah Building to coincide with the second anniversary of the siege at Waco.

Until the terrorist attacks of September 11, 2001, the Oklahoma City attack was regarded as the worst terrorist act in U.S. history. Many in the black community, however, commonly refer to a much earlier example of home grown terrorism in Oklahoma — the Tulsa Race Riot of May 31, 1921, when a white mob destroyed the thriving black community of Greenwood, known as Black Wall Street. As many as 300 people were killed, with 35 square blocks razed and 3,000 homes destroyed. For African-Americans, terrorism is not a new phenomenon.

WATCH NBC’S REPORT ON THE BOMBING FROM APRIL 19, 1995
[MSNBCMSN video=”http://www.msnbc.msn.com/id/32545640″ w=”592″ h=”346″ launch_id=”36557170″ id=”msnbc502094″]

Visit msnbc.com for breaking news, world news, and news about the economy

“Let us let our own children know that we will stand against the forces of fear,” said then-President Clinton at the memorial service for the Oklahoma City victims, just four days after the bombing. “When there is talk of hatred, let us stand up and talk against it. When there is talk of violence, let us stand up and talk against it. In the face of death, let us honor life. As St. Paul admonished us, Let us ‘not be overcome by evil, but overcome evil with good.’”

Fifteen years later, Clinton is warning us of the parallels between today and 1995. Back then, he suggests, anti-government sentiment, the vilification of government officials and a growing militia movement created a climate that led to the bombing of the Murrah Building.

“I remember when Newt Gingrich, shortly after becoming speaker, said that Hillary and I were the enemies of normal Americans. It didn’t bother me a bit,” the former president said in a recent speech. “But what we learned from Oklahoma City is not that we should gag each other or reduce our passion from the positions we hold — but that the words we use really do matter, because there’s this vast echo chamber and they go across space and they fall on the serious and the delirious alike. They fall on the connected and the unhinged alike.”

Last year, the Department of Homeland Security issued “Right-wing Extremism: Current Economic and Political Climate Fueling Resurgence in Radicalization and Recruitment.” The report warned that the current economic recession and the election of the first black president have provided fertile recruitment opportunities for extremist right-wing and white supremacist groups. The current environment could lead to confrontations between these radicals and government authorities, such as the Oklahoma City bombing and other examples of domestic terrorism in the 1990s. These right-wing, anti-government forces are united by their hatred of Latinos and immigrants, hostility towards gun control laws, and racial resentment towards President Obama.

Meanwhile, a new report from the Southern Poverty Law Center has documented a dramatic increase in extremist groups in just one year. These groups, which range from Klansmen, neo-Nazis and neo-Confederates to homophobes, vigilantes and Holocaust deniers, have exploited popular anger with their outrageous anti-government conspiracy theories.

In 2009, the number of active patriot groups jumped 244 percent, from 149 groups in 2008 to 512 groups in 2009. Much of that increase was due to the growth of the paramilitary organizations called militias – which increased from 42 groups in 2008 to 127 in 2009.

“This extraordinary growth is a cause for grave concern,” said the SPLC’s Mark Potok. “The people associated with the Patriot movement during its 1990s heyday produced an enormous amount of violence, most dramatically the Oklahoma City bombing that left 168 people dead.”

In addition to Patriot and militia groups, the U.S. is witnessing a record number of racist hate groups — from 926 in 2008 to 932 in 2009 — in a decade when hate groups jumped 55 percent. Meanwhile, “nativist extremist” groups not only oppose current immigration policy, but these vigilantes take matters into their own hands and harass presumed immigrants. Nativists increased 80 percent in one year, from 173 in 2008 to 309 last year.

In total, according to the SPLC, extremist groups increased 40 percent in 2009, from 1,248 groups in 2008 to 1,753 last year. We are reaping the consequences of their rise, with right-wing violence that harkens back to the 1990s: The murder of six police officers since the start of the Obama administration, racist skinhead plots to assassinate the president, and bomb plots on the part of anti-government, racist and survivalist groups.

What is particularly disturbing about the rise of the patriot movement is their success in penetrating the mainstream and becoming part and parcel of conservative American politics, something which had not occurred in the 1990s.

“The ‘tea parties’ and similar groups that have sprung up in recent months cannot fairly be considered extremist groups, but they are shot through with rich veins of radical ideas, conspiracy theories and racism,” the SPLC report notes. Consider high-profile personalities with large followings that embrace the anti-government rhetoric and conspiracy theories of the patriot movement, such as Rep. Michele Bachmann (R, Minn), who suggested Obama was planning re-education camps for young people, and FOX News host Glenn Beck, who promoted the conspiracy theory that the Federal Emergency Management Agency (FEMA) is operating secret concentration camps.

The Oath Keepers — a militia group consisting of current and ex-soldiers and police officers — similarly warns about concentration camps, a coming dictatorship, and a “New World Order.” This organization, which considers President Obama “an enemy of the state”, is co-sponsoring the Second Amendment March on Washington set for, not surprisingly, April 19th.

Birthers, who have been legitimized by conservative news outlets and members of Congress, believe that President Obama was born in a foreign country and is not a U.S. citizen. James Von Brunn, the white supremacist who opened fire and killed a security officer at the National Holocaust Museum, was part of the Birther movement, which has racist and anti-Semitic origins.

Meanwhile, Oklahoma legislators and tea party members have proposed the formation a volunteer militia group to defend against the federal government. And the Colorado Court of Appeals has rejected on Second Amendment grounds the University of Colorado’s ban on students carrying weapons on campus.

Fifteen years after the Oklahoma City bombing, the extremist groups are back and they’re bigger and badder than ever. And this time, they are coalescing, working from the same page, and enjoying support from some circles in government and the media. Once again, we have failed to learn from the lessons of history. Are “the dark clouds of fascism gathering” in America, as Noam Chomsky suggests? Although we must hope he is wrong, perhaps he has a point.

Nevertheless, we should all make it a point to watch our back.