That's pretty dreadful, almost sounds like the bank officials were chancing their arms. I'm not sure why they would do this unless its a tactic they use to try and blow the cover on some customers who may have additional unreported funds stashed away somewhere.
As a starting point I think your BIL should write down all the accusations that were made against him at the meeting. Because this was all verbal, if it is ever challenged its his word against theirs, but at least by writing it down now while its fresh in his mind he has his own record of what was said.
I presume their is a relationship manager of some description who is your BILs normal point of contact when dealing with the bank. I think your BIL should try and contact him regardless of whether or not he was one of the 3 that he met. Its very awkward because he has immediate financing problems which he needs to try and get sorted out asap. He should again deny as lies all the accusations that were made against him and again seek their assistance to help him overcome this short term problem.
If the bank do not entertain him he should formally complain to them, setting out the accusations made against him and his assertion that they are totally without foundation.
Under the Code for Lending to SMEs [broken link removed] they are supposed to work with SMEs in financial difficulties, so if they are not seen to do this he can complain to the Central Bank or the Credit Review Office.