The government has an obligation to protect unpopular speech. In the case Terminiello v. Chicago (1949), the Supreme Court ruled that “a function of free speech under our system of government is to invite dispute. It may indeed best serve its high purpose when it induces a condition of unrest, creates dissatisfaction with conditions as they are, or even stirs people to anger.” In the case Forsyth v. County v. Nationalist Movement (1992), the Supreme Court ruled that the government could not prevent or unduly burden speech merely because it might prove “unpopular with bottle throwers” or “because it might offend a hostile mob.” A situation in which the authorities allow a person or group to shut down the expression of a speaker is called a “heckler’s veto.”

Further reading:

Rejecting the Heckler’s Veto

Disinvitation Season: Protected Counter-Speech or Heckler’s Veto?