Black Lives Matter Leader DeRay McKesson Sues Jeanine Pirro, FOX News (UPDATE)

6:15 PM PT -- A FOX News spokesperson tells TMZ ... “We informed Mr. McKesson's counsel that our commentary was fully protected under the First Amendment and the privilege for reports of judicial proceedings. We will defend this case vigorously.”

DeRay McKesson -- one of the leaders of the Black Lives Matter movement -- is suing FOX News personality Jeanine Pirro for saying he directed protesters to attack a police officer.

McKesson says Pirro was on "FOX & Friends" on September 28, discussing a lawsuit filed by the cop against BLM. According to the suit, Pirro made a series of outrageous and false statements about him.

In the docs, obtained by TMZ, DeRay says Pirro blamed him for directing the violence, and added, "You've got a police officer who was injured, he was injured at the direction of DeRay McKesson."

DeRay believes Pirro made her statements knowing they were false -- and it's damaged his rep and endangered him as a civil rights activist. As we reported, a federal judge ruled McKesson was expressing his right to free speech at the demonstration, and it wasn't his fault the officer got hurt.

DeRay's suing both Pirro and FOX News for defamation.