It would be misleading to say that Hustler v. Falwell extended the scope of First Amendment speech protections. What the Supreme Court did, essentially, was to preserve the scope that already existed, which they did by rejecting an effort by the Appeals Court to allow a public figure, absent a finding of libel, to recover on a claim of emotional distress.
As the United States Supreme Court declared in the landmark case of Hustler v. Falwell , an advertising parody which portrayed the leader of the MOral Majority as having engaged in a drunken incestuous rendezvous with his other, could not reasonably have been interpreted as stating actual facts about him.
Hustler Magazine v. Falwell is a classic First Amendment case. Its antagonists could have been selected by central casting to embody the fundamental constitutional tension between anarchich self-expression and strict civic virtue.