Which important supreme court decision established the principle that “it is the right of the viewers and listeners, not the right of the broadcasters, which is paramount,” effectively granting the upper hand to the audience when its interests conflict with those of broadcasters?

Red Lion Broadcasting v. FCC  (1969)

A radio station operated by Red Lion Broadcasting ran a broadcast segment in which Reverend Billy James Hargis expressed harsh criticisms of Fred Cook, who had authored a book that spoke against presidential candidate Barry Goldwater.  Cook insisted that he should receive free air time to respond to Hargis' allegations against him.  The FCC had said that the station needed to give Cook opportunity to respond on air.  When the case made its way to the Supreme Court, the court sided with Cook's perspective and the FCC.

Islam was founded in the same region