Why did the pullman palace car company only employ african american porters?

By forming the first black labor union, the Brotherhood of Sleeping Car Porters, Pullman porters also laid the groundwork for the Civil Rights Movement, which began in the 1950s. ... The Pullman Company went out of business in 1969, and the railroads no longer followed the practice of hiring only black men as porters.

“Pullman porters would bring African-American newspapers like the Chicago Defender or Pittsburgh Courier back to their communities,” Crew tells Smithsonian.com. Those newspapers, he said, gave Southerners information on how and where they could escape the segregation and violence they experienced at home.

Though those social gains had a cost, Crew sees the Pullman porters as part of a larger context of African-American mobility and community. “They figured out how to understand the mores of the larger society and maintain a sense of dignity,” he tells Smithsonian.com. That history—one of resilience, resistance and pride—is well worth remembering.

In other words, It was advertised by African- Americans, worked by African Americans, and will be remembered by African-Americans. They worked hard, they barely ate, they barely slept. This is to be for the heritage. The African-Americans only employ their own kind because they want to show the community they are a family. They do things together. They work together. And they don't need anyone else to do it for them. They are hard workers, and they will continue working hard for something they think and know is important.

If it's not useful, feel free to report for mistake in answer. -_-

either b) they were often feared and despised by other native cultures. or

c) their obsession allowed them to coexist with many other native cultures because of their peaceful nature.