No, the government can't limit speech in the same manner as a private individual. See Pickering vs Board of Education; it was not permissible to sanction Pickering (a teacher) for his speech (as a citizen) criticizing the Board of Ed. They could only sanction him if he criticized the board of ed <i>while carrying out his teaching duties</i> (which he didn't).<p>Similarly, if my students criticize me during class, I can say "shut up unless you want to talk about linear algebra." If they criticize me on ratemyprofessor.com or in the hallway, I'm out of luck.<p>Google, however, can fire their employees even for complaining about Marisa in a bar.<p>As for whether students should be permitted to shout "nigger" out their window, the answer should not change if they should "asslicker" out the window. The government can ban shouting out the window, they just can't ban shouting <i>certain things but not others</i>. They can even ban fighting words (shouting strong insults at a specific person) as long as they do so in an all-or-nothing manner (they can't ban "nigger" but not "asslicker").