If you owed him money and never paid, either because of it being discharged in bankruptcy or just because you defaulted, he is entitled to his opinion that you screwed him. He's entitled to publicly state that fact. In the case of a Chapter 7, it's unclear what ongoing business that you have that is even capable of being defamed.

It's not a violation of the discharge injunction to complain that you didn't pay your debts. The injunction only covers attempts to collect the debt.

He might be guilty of violating the anti-cybersquatting, but that isn't a crime NOR even something you can get civil relief on. It's a feature of the Domain Name rules. The problem here again is that you HAVE NO LEGITIMATE CLAIM ON THE COMPANY NAME it would appear any more than he does. Of course, you can spend the several THOUSAND dollars to initiate a UDRP action and possibly prevail and all that will do is have the domain name awarded to you.

It appears to be plain jane CONSTITUTIONALLY PROTECTED FREE SPEECH. You are responsible for your actions. Bankruptcy only wipes out the responsibility to pay the debt, NOTHING ELSE.