Should WBC be able to yell GOD HATES GAYS in a movie theater while you are watching a film?
The answer is no because the purpose of that speech is used as a device to interrupt the film. The people paid to watch the art that is shown in the form of a movie and even a church does not have the right to keep you from enjoying your movie without interruption.
Should you be allowed to stand and yell and scream and make a fuss during a speech by Ann Coulter here at university? No because doing so is designed to interrupt Ann Coulter’s speech and the rights of the audience to listen to it. The courts call this a “heckler’s veto” and that type of interruption has never been considered protected speech. The “heckler’s veto” does not serve the purpose of delivering a substantive view, but rather the yelling is used as a device to interrupt an event.
Should they be allowed to have a GOD HATES GAYS rally in the middle of a 4 lane super highway? The answer is no because the event is designed to interrupt others with the conveyance of an idea being a distant secondary purpose.
In this case the speech by WBC is designed to interrupt another. WBC used the disruption for the purpose of interrupting the funeral event that other people paid for.
A funeral is a cultural and (usually) religious exercise of expression and is protected by the First Amendment just as the First Amendment protects you when you pay to see a film or when you watch a speech by Ann Coulter and the police physically remove someone who wishes to do a “hecklers veto” by interrupting the event.
WBC should be allowed to protest before and after the service, they may also do so away from the service while it is going on, but not within vocal shot of the service while it is going on.