Actually the phrase does not include a parentheses about race. The declaration and constitution don’t make any mention of race until a Supreme Court decision in the 1850’s. That doesn’t mean racism wasn’t practiced; it most certainly was, by racist white men. In other words, it’s not the fault of the ideals but of the practices of the people in power who did not bring those ideals into existence and ignored them. I’m making this point not because I disagree that white men weren’t responsible for slavery, but because a minority of whites fought for abolition of slavery from the very beginning and continued to fight for it against the majority who,did not practice the ideal of democracy. It is not a struggle that ended, but changing mentality lies more along “the long arc of justice” as,mentioned by King.