Napolitano points to a footnote in the document that defines “rightwing extremism” as “groups and individuals that are dedicated to a single issue, such as opposition to abortion or immigration.”There is great fear among the liberals that the "right wing extremists" are domestic terrorists.
“Rightwing extremists will attempt to recruit and radicalize returning veterans in order to exploit their skills and knowledge derived from military training and combat.”
This parable may help you see the ridiculousness of the above idea:
A man that rapes 3 dozen little girls would see someone who looks at pornography as simply a moderate. The rapist would see a monogamous man, who is faithful to his wife as an extremist.
The liberals have spent their time raping every line of the Constitution, but have the gall to brand law-abiding citizens as the terrorists.
I suppose it all depends on your perspective.