Hate groups and radical right - same thing? [Help a sister out, please]

The Southern Poverty Law Center has released a report that shows hate groups in the United States top 1,000 for the first time. This is a clear reminder that organized hate, among other things, is on the rise, but the thing that struck me was in the opening paragraph of the announcement of the report:

The number of active hate groups in the United States topped 1,000 for the first time and the antigovernment “Patriot” movement expanded dramatically for the second straight year as the radical right showed continued explosive growth in 2010.

[Insert noise made by cute animated puppy that is suddenly confused]

I imagined posting a link to this report on this very jarring statistic, but the first thing I though of was how at least 5 people I know would never make it past that first paragraph and how quickly, the conversation would ignore the very important and jarring statistic and instead focus on the interchangeable use of the term "hate group" and the term "radical right."

I read the rest of the release, hoping that at some point they mentioned the research behind this automatic correlation, but to no avail.

Can someone break this down for me? Because, really...

update:

NPR has a report on the findings without the sloppy conjecture.