"In 1979, the NLRB issued its Atlantic Steel decision, which established the test for determining when an employee’s otherwise protected speech towards management becomes too extreme to remain protected. This standard considered:

(1) the place of the discussion

(2) the subject matter of the discussion

(3) the nature of the employee’s outburst

(4) whether the outburst was, in any way, provoked by an employer’s unfair labor practice."

You should probably have added this for nuance, so people don't misunderstand you and get the idea that name calling per se is protected.