You actually see this a lot, people letting the Wall St. bandits off the hook with the excuse "Hey, it wasn't illegal!"
a) A lot of it was, yeah
b) And it doesn't matter if it's illegal if nobody's around to enforce the law
c) As you point out, something can be legal yet ethically odious
d) A lot of it that was legal is because Wall St. is literally writing the laws that govern it, which is absurd