SPLC fits its own definition of a hate group.

Heidi Beirich, the head of the SPLC’s Intelligence Project, says the group’s criteria are clear and transparent, pointing to the definition published on its website of hate groups as ones that “have beliefs or practices that attack or malign an entire class of people, typically for their immutable characteristics.” While Beirich cites several left-wing organizations the SPLC has designated as “hate groups,” she concedes that the SPLC prioritizes the other end of the political spectrum. “We are focused, whether people like it or not, on the radical right,” she says. “We believe that it’s uniquely threatening to democracy.”

Even Politico, the left biased news source questions their credibility

https:// www.politico.com/magazine/story/2017/06/28/morris-dees-splc-trump-southern-poverty-law-center-215312