No workplace is perfect. Co-workers can and do get into arguments with other employees and may say things that are downright offensive. But courts expect employees to have relatively thick skins, at least when the perceived harassment is coming from co-workers and not a supervisor.
As long as you are confident that the same co-worker won’t lash out again (because you punished the behavior), don’t lose too much sleep over one incident.
Recent case: Ricky worked as a driver. When a Hispanic co-worker told Ricky that Mexican immigrants work harder than “white people,” he took offense.
Later, after he was fired for unrelated reasons, Ricky sued, alleging he had worked in a hostile environment.
But the court quickly dismissed the case. It reasoned that a one-time comment by a co-worker was not enough to maintain a lawsuit. (Hildebrand v. PBM Graphics, No. 5:13-CV-15, ED NC, 2013)