Mark Potok is the director of the Southern Poverty Law Center's "Intelligence Project". In that role he issues McCarthyite declarations that some organization are "hate groups" and acts as a quote source for an endless series of MSM articles. The SPLC is indirectly linked to the Mexican government, and much of their recent work consists not of fighting the Klan but instead of fighting those who want to - unlike the SPLC - enforce our immigration laws.
If you trust his judgment, read about how he misled about hate crime statistics.