Taye Diggs says Rodney Harrison's "not black" attack on Colin Kaepernick is straight out of the 1800's ... saying it's the same type of talk slave masters used to divide their black slaves.
Diggs -- the father of a mixed son -- blasted Harrison in a statement to TMZ Sports ... chiding the ex-NFL star's assertion that Kaep didn't understand the hardships of black people.
"I'm still baffled at the idea that one person is justified in telling another person what suffering is, regardless of race or hue or skin or anything else.