To bring a successful defamation claim, a defendant must have published a false statement of fact (not just an opinion) concerning the plaintiff, that caused damage to their reputation.
The defense of opinion protects individuals from being held liable for defamation in cases where the statements made were opinions rather than false statements of fact. This defense is based on the First Amendment right to freedom of speech, which recognizes that opinions are a form of protected speech. In order for a statement to be considered an opinion, it must be a statement that can be neither proven nor disproven.