Why might African American activists and workers have used the phrase "I Am a Man" on their protest signs? Support your answer with evidence from the text.

The men worked long hours for low wages, with no overtime pay and no paid sick leave. Injuries on the job could lead to their getting fired. If they didn’t work, they didn’t get paid. Most of them made 65 cents per hour.
“We felt we would have to let the city know that because we were sanitation workers, we were human beings. The signs we were carrying said ‘I Am a Man,’ ” James Douglas, a sanitation worker, recalled in an American Federation of State, County and Municipal Employees documentary. “And we were going to demand to have the same dignity and the same courtesy any other citizen of Memphis has.”

What is this from lol