A defense to a claim of defamation is that the statement is true. If you can prove that your statement is true, then you have a defense. Also, he has to show that he was somehow damaged by your claims. You need to contact a Florida Attorney to review your options. Please understand that no matter what, you might still get sued, and it might cost you some $$$ to put up a defense, but if your statements were true, then at least you have a defense.
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If there was a valid conviction then you have an absolute defense. Your question bring up an interesting situation. Be careful what you say on the internet. While you can delete it the comments are there forever somewhere in internet space.
In Florida, there are various defenses and privileges that can be asserted in response to a defamation suit. But most often, these threatened lawsuits do not result in any actual complaint being filed in a court. It's easy to talk about filing a suit, but lawyers are expensive. Moreover, the many more people will find about about the owner's alleged criminal if a public lawsuit is filed, than if the owner took no action. Google the Streisand Effect. Naturally, if you are sued, you'll need to hire a lawyer to defend the case, but it would seem to be in the business owner's best interests to let it go.
Disclaimer: The foregoing does not constitute legal advice or form an attorney/client relationship. Please contact an attorney for formal legal advice on any specific matter.