I suspect that people don't fall into such neat categories. You could pose a similar question re: lawyers whose bread and butter is protecting and representing people associated with organised crime (the kind of individuals represented by Maury from The Wire or Neil Mink from The Sopranos). Are they lawyers who developed a slippery version of ethics & morality, or people with loose ethical standards who entered law?
I'd bet good money that the truth is usually quite banal: these individuals make a series of small and highly contingent decisions over time that gradually push them in the direction of criminality or culpability, reinforced over time by social & financial reward for doing so.