Fraud is one of the actions which are actionable under Natural Law. If someone claims fraud, they are welcome to prove their case in a natural law court. Even in the positive law courts the truth is allowed to disprove claims of fraud. If you are telling the truth, you are not supposed to be liable for fraud. Truth is truth.

Rothbardian_fanatic

Politics_And_Law

Freedom of Speech and Defamation Laws

There's a little scope for fraud claims to enter the picture, in some cases. However, for the most part, the only consistent rule is that each person is allowed to say what they want to say.