Robert A. Caro, Master of the Senate: The Years of Lyndon Johnson, Volume III: 

“Whenever I was late, no matter what the reason, Johnson called me a lazy, good-for-nothing n****r,” Parker wrote. And there was an incident that occurred one morning in Johnson’s limousine while Parker was driving him from his Thirtieth Place house to the Capitol. Johnson, who had been reading a newspaper in the back seat, “suddenly lowered the newspaper and leaned forward,” and said, “‘Chief, does it bother you when people don’t call you by name?’” Parker was to recall that “I answered cautiously but honestly, ‘Well, sir, I do wonder. My name is Robert Parker.’” And that was evidently not an answer acceptable to Johnson. “Johnson slammed the paper onto the seat as if he was slapping my face. He leaned close to my ear. ‘Let me tell you one thing, n****r,’ he shouted. ‘As long as you are black, and you’re gonna be black till the day you die, no one’s gonna call you by your goddamn name. So no matter what you are called, n****r, you just let it roll off your back like water, and you’ll make it. Just pretend you’re a goddamn piece of furniture.’” 

Parker found that incident in Johnson’s limousine difficult to explain or forgive. Years later, as he stood beside Lyndon Johnson’s grave thinking of all Johnson had done for his people, Parker would say he was “swirling with mixed emotions.” Lyndon Johnson, he would write, had rammed through Congress “the most important civil rights laws this country has ever seen or dreamed possible.” Because of those laws, Parker would write, he felt, at last, like a free man. “I owed that freedom to him…. I loved the Lyndon Johnson who made it possible.” But remembering the scene in the limousine — and many other scenes — Parker was to write that on the whole working for Johnson was “a painful experience. Although I was grateful to him for getting me a job I was afraid of him because of the pain and humiliation he could inflict at a moment’s notice. I thought I had learned to fight my bitterness and anger inside…. But Johnson made it hard to keep the waves of bitterness inside… But I had to swallow or quit. If I quit, how would I support my family? I chose survival and learned to swallow with a smile.” And, Parker would write, “I hated that Lyndon Johnson.” 

Here is Robert Parker’s book.