Ed Morrissey defends the right:
[O]ur criticism was that the DHS report didn’t focus on known, specific threats, instead making generalized threats about abortion opponents and other vague and broad generalizations about conservative issues. In fact, it never mentioned Holocaust denial at all, nor did it mention anti-semitism at all, either; those terms don’t appear at all in the report.
From the report (pdf):
Rightwing extremist chatter on the Internet continues to focus on the economy, the perceived loss of U.S. jobs in the manufacturing and construction sectors, and home foreclosures. Anti-Semitic extremists attribute these losses to a deliberate conspiracy conducted by a cabal of Jewish “financial elites.” These “accusatory” tactics are employed to draw new recruits into rightwing extremist groups and further radicalize those already subscribing to extremist beliefs. DHS/I&A assesses this trend is likely to accelerate if the economy is perceived to worsen.
Italics mine. Another paragraph from the report:
A recent example of the potential violence associated with a rise in rightwing extremism may be found in the shooting deaths of three police officers in Pittsburgh, Pennsylvania, on 4 April 2009. The alleged gunman’s reaction reportedly was influenced by his racist ideology and belief in antigovernment conspiracy theories related to gun confiscations, citizen detention camps, and a Jewish-controlled “one world government.”
Morrissey later updates:
I wrote that the report didn’t mention anti-Semitism, but it actually did. It talked about anti-Semitic extremists. I did a search on “semitism” and not “Semitic”, and I should have done both. Sloppy work. I apologize.
But he gives no new rationale for opposing the DHS report.