From the way the OP lays it out it seems to me they were willing to place trust in the new guy. It was only after the lengthy rant started that the uneasiness started setting in.
A customer at any business other than auto repair would feel the same way. Imagine listening to the receptionist at a doctor’s office, a CSM at Wal Mart, or home remodeling contractor ranting and bad mouthing fellow employees, management, or the competition.