The Westboro Baptist Church (who are really a cult) have targeted many groups including homosexuals, military personnel, and even the children of the Sandy Hook Elementary shooting.
By committing slander (written defamation of another person) and libel (spoken defamation of another person), the Westboro Baptist Church has broken the law and needs to be shut down.
They are destroying the personal rights of other human beings, and that is in fact NOT protected by the First Amendment.