Michael Wittmer, Swimmer and McLean's coworker who recorded the conversation, said that comments like that have "been going on a long time" at the water department.
"The employees that work with me haven't been too happy with me," Wittmer said to Fox 25. "They feel like they were misled, but they weren't misled. They just shouldn't have been saying what they were saying."
Wittmer said that after giving the tape to Tulsa World, a local publication, he went to work only to realize that his key would not open the door.
"I thought it was real disrespectful," Wittmer said before adding that MLK deserves to be honored no "matter what color or what race you are."
Reverend Roger Cutler, leader of the NAACP chapter in Muskogee, Oklahoma, also found the remarks disrespectful.
"It is appalling as a citizen of this state in this day and age to still have to deal with this type of racism," Cutler said. "They don't hate black people, well then why would you use a term that is derogatory towards someone you claim not to hate?"
City of Warner officials reportedly hosted a town hall meeting following the incident, where they addressed the resignations and promised an investigation into the incident.