There’s always been a thin line between the definition of a shrewd business policy and an unethical policy.
It’s shrewd business from his perspective if a car salesman doesn’t disclose a problem with the car that he knows exists. Billions of dollars in derivatives were sold: it was a shrewd financial product. Was it unethical that most derivative sellers didn’t explain what customers really were buying? In many cases the sellers didn’t know themselves what they were selling.