Western woods, that statement is both bad law and comes disturbingly close to pandering to the ignorant minority that rants about "hurt feelings."

As you are well aware, the law requires both employers and those who operate schools to do what they can to prevent the poisoned atmosphere of racism.  This goes well beyond actual threats of violence (although making a joke about lynching black students can be seen as an actual threat.)

You may recall the Supreme Court's unanimous decision in Ross, which involved a teacher's off-duty anti-semitic writings.  As the court wrote: 
"What this evidence discloses is a poisoned educational environment in which Jewish children perceive the potential for misconduct and are likely to feel isolated and suffer a loss of self-esteem on the basis of their Judaism."