Burning outrage over Congressional redistricting in Tennessee is exploding in that state's capital ... where state Rep. Justin Jones set fire to Confederate flag.

Justin was protesting Tennessee Republicans approving a new Congressional map Thursday -- splitting up a majority-Black district in Memphis -- when he joined a crowd marching and chanting through the Capitol, held up a printout of the rebel flag ... and lit it up.

While still holding the burned flag -- which had "We will not go back" written along the edge -- Justin told The Tennessean, "They're taking us backwards to this type of environment where Black folks are not treated with equal representation, where we're pre-1965."

He feels Republicans are "dragging us backwards in history" with this vote, saying on Instagram, ... "When I walked into the building it was 2026, and when I walked out it was pre-1965. This racial power grab against Black voters is purely rooted in control and elimination of their voices in our democracy."

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The redistricting splits Memphis and Shelby County into 3 separate districts ... breaking up the state's only Democratic district. Governor Bill Lee signed it into law almost immediately.

Justin believes this is about to lead to the "largest loss of Black legislators and Black representation since the end of Reconstruction."

This is the first redistricting vote since the Supreme Court weakened the Voting Rights Act's protections against racial gerrymandering. The NAACP has filed a lawsuit to try to block the redistricting ... but Justin is opting to fight fire with literal fire.