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President Trump and the National Rifle Ass'n are stereotyping all black men as dangerous, and the proof is their silence over the killing of Philando Castile ... so says Congressman Cedric Richmond.

Richmond was on Capitol Hill Thursday when our photog asked about gun advocates like the President and the NRA ... both of which had nothing to say about the 2nd Amendment when it came to the killing of Castile, who told cops he was carrying a legal gun.

As you know, the cop shot Castile 7 times at point-blank range, claiming he feared for his life.

The congressman -- who also chairs the powerful Black Caucus -- is incredulous Trump and the NRA have not defended Castile's right to bear arms.